diff --git a/packages/gatsby-plugin-sass/README.md b/packages/gatsby-plugin-sass/README.md
index 83ad3d828bc8d..2a7cb87e8e087 100644
--- a/packages/gatsby-plugin-sass/README.md
+++ b/packages/gatsby-plugin-sass/README.md
@@ -64,6 +64,23 @@ plugins: [
 ]
 ```
 
+### additionalData
+
+Prepends Sass code before the actual entry file. In this case, the `sass-loader` will not override the data option but just prepend the entry's content. You might use this to prepend things like environmental variables (as Sass variables) or even prepend a global Sass import to be used in other Sass files (functions, mixins, variables, etc.).
+
+See [webpack's sass-loader documentation](https://webpack.js.org/loaders/sass-loader/#additionaldata) for reference.
+
+```javascript:title=gatsby-config.js
+plugins: [
+  {
+    resolve: `gatsby-plugin-sass`,
+    options: {
+      additionalData: "$env: " + process.env.NODE_ENV + ";",
+    },
+  },
+]
+```
+
 ### Alternative Sass Implementations
 
 By default, the Dart implementation of Sass (`sass`) is used. To use the implementation written in Node (`node-sass`), you can install `node-sass` instead of `sass` and pass it into the options as the implementation:
diff --git a/packages/gatsby-plugin-sass/src/__tests__/__snapshots__/gatsby-node.js.snap b/packages/gatsby-plugin-sass/src/__tests__/__snapshots__/gatsby-node.js.snap
index 41deb873c2b55..31a5f203cd130 100644
--- a/packages/gatsby-plugin-sass/src/__tests__/__snapshots__/gatsby-node.js.snap
+++ b/packages/gatsby-plugin-sass/src/__tests__/__snapshots__/gatsby-node.js.snap
@@ -17,6 +17,7 @@ exports[`gatsby-plugin-sass Stage: build-html / No options 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -30,6 +31,7 @@ exports[`gatsby-plugin-sass Stage: build-html / No options 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -69,6 +71,7 @@ exports[`gatsby-plugin-sass Stage: build-html / PostCss plugins 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -82,6 +85,7 @@ exports[`gatsby-plugin-sass Stage: build-html / PostCss plugins 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -121,6 +125,7 @@ exports[`gatsby-plugin-sass Stage: build-html / Sass options 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {
                           "includePaths": Array [
                             "absolute/path/a",
@@ -139,6 +144,7 @@ exports[`gatsby-plugin-sass Stage: build-html / Sass options 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {
                           "includePaths": Array [
                             "absolute/path/a",
@@ -183,6 +189,7 @@ exports[`gatsby-plugin-sass Stage: build-html / css-loader options 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -196,6 +203,7 @@ exports[`gatsby-plugin-sass Stage: build-html / css-loader options 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -235,6 +243,7 @@ exports[`gatsby-plugin-sass Stage: build-html / css-loader use commonjs 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -248,6 +257,7 @@ exports[`gatsby-plugin-sass Stage: build-html / css-loader use commonjs 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -287,6 +297,7 @@ exports[`gatsby-plugin-sass Stage: build-html / sass rule modules test options 1
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -300,6 +311,7 @@ exports[`gatsby-plugin-sass Stage: build-html / sass rule modules test options 1
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -339,6 +351,7 @@ exports[`gatsby-plugin-sass Stage: build-html / sass rule test options 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -352,6 +365,7 @@ exports[`gatsby-plugin-sass Stage: build-html / sass rule test options 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -392,6 +406,7 @@ exports[`gatsby-plugin-sass Stage: build-javascript / No options 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -407,6 +422,7 @@ exports[`gatsby-plugin-sass Stage: build-javascript / No options 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -447,6 +463,7 @@ exports[`gatsby-plugin-sass Stage: build-javascript / PostCss plugins 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -462,6 +479,7 @@ exports[`gatsby-plugin-sass Stage: build-javascript / PostCss plugins 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -502,6 +520,7 @@ exports[`gatsby-plugin-sass Stage: build-javascript / Sass options 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {
                           "includePaths": Array [
                             "absolute/path/a",
@@ -522,6 +541,7 @@ exports[`gatsby-plugin-sass Stage: build-javascript / Sass options 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {
                           "includePaths": Array [
                             "absolute/path/a",
@@ -567,6 +587,7 @@ exports[`gatsby-plugin-sass Stage: build-javascript / css-loader options 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -582,6 +603,7 @@ exports[`gatsby-plugin-sass Stage: build-javascript / css-loader options 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -622,6 +644,7 @@ exports[`gatsby-plugin-sass Stage: build-javascript / css-loader use commonjs 1`
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -637,6 +660,7 @@ exports[`gatsby-plugin-sass Stage: build-javascript / css-loader use commonjs 1`
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -677,6 +701,7 @@ exports[`gatsby-plugin-sass Stage: build-javascript / sass rule modules test opt
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -692,6 +717,7 @@ exports[`gatsby-plugin-sass Stage: build-javascript / sass rule modules test opt
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -732,6 +758,7 @@ exports[`gatsby-plugin-sass Stage: build-javascript / sass rule test options 1`]
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -747,6 +774,7 @@ exports[`gatsby-plugin-sass Stage: build-javascript / sass rule test options 1`]
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -787,6 +815,7 @@ exports[`gatsby-plugin-sass Stage: develop / No options 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -802,6 +831,7 @@ exports[`gatsby-plugin-sass Stage: develop / No options 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -842,6 +872,7 @@ exports[`gatsby-plugin-sass Stage: develop / PostCss plugins 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -857,6 +888,7 @@ exports[`gatsby-plugin-sass Stage: develop / PostCss plugins 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -897,6 +929,7 @@ exports[`gatsby-plugin-sass Stage: develop / Sass options 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {
                           "includePaths": Array [
                             "absolute/path/a",
@@ -917,6 +950,7 @@ exports[`gatsby-plugin-sass Stage: develop / Sass options 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {
                           "includePaths": Array [
                             "absolute/path/a",
@@ -962,6 +996,7 @@ exports[`gatsby-plugin-sass Stage: develop / css-loader options 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -977,6 +1012,7 @@ exports[`gatsby-plugin-sass Stage: develop / css-loader options 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -1017,6 +1053,7 @@ exports[`gatsby-plugin-sass Stage: develop / css-loader use commonjs 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -1032,6 +1069,7 @@ exports[`gatsby-plugin-sass Stage: develop / css-loader use commonjs 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -1072,6 +1110,7 @@ exports[`gatsby-plugin-sass Stage: develop / sass rule modules test options 1`]
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -1087,6 +1126,7 @@ exports[`gatsby-plugin-sass Stage: develop / sass rule modules test options 1`]
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -1127,6 +1167,7 @@ exports[`gatsby-plugin-sass Stage: develop / sass rule test options 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -1142,6 +1183,7 @@ exports[`gatsby-plugin-sass Stage: develop / sass rule test options 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -1181,6 +1223,7 @@ exports[`gatsby-plugin-sass Stage: develop-html / No options 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -1194,6 +1237,7 @@ exports[`gatsby-plugin-sass Stage: develop-html / No options 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -1233,6 +1277,7 @@ exports[`gatsby-plugin-sass Stage: develop-html / PostCss plugins 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -1246,6 +1291,7 @@ exports[`gatsby-plugin-sass Stage: develop-html / PostCss plugins 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -1285,6 +1331,7 @@ exports[`gatsby-plugin-sass Stage: develop-html / Sass options 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {
                           "includePaths": Array [
                             "absolute/path/a",
@@ -1303,6 +1350,7 @@ exports[`gatsby-plugin-sass Stage: develop-html / Sass options 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {
                           "includePaths": Array [
                             "absolute/path/a",
@@ -1347,6 +1395,7 @@ exports[`gatsby-plugin-sass Stage: develop-html / css-loader options 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -1360,6 +1409,7 @@ exports[`gatsby-plugin-sass Stage: develop-html / css-loader options 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -1399,6 +1449,7 @@ exports[`gatsby-plugin-sass Stage: develop-html / css-loader use commonjs 1`] =
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -1412,6 +1463,7 @@ exports[`gatsby-plugin-sass Stage: develop-html / css-loader use commonjs 1`] =
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -1451,6 +1503,7 @@ exports[`gatsby-plugin-sass Stage: develop-html / sass rule modules test options
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -1464,6 +1517,7 @@ exports[`gatsby-plugin-sass Stage: develop-html / sass rule modules test options
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -1503,6 +1557,7 @@ exports[`gatsby-plugin-sass Stage: develop-html / sass rule test options 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
@@ -1516,6 +1571,7 @@ exports[`gatsby-plugin-sass Stage: develop-html / sass rule test options 1`] = `
                     Object {
                       "loader": "<PROJECT_ROOT>/node_modules/sass-loader/dist/cjs.js",
                       "options": Object {
+                        "additionalData": undefined,
                         "sassOptions": Object {},
                         "sourceMap": undefined,
                       },
diff --git a/packages/gatsby-plugin-sass/src/__tests__/gatsby-node.js b/packages/gatsby-plugin-sass/src/__tests__/gatsby-node.js
index 74a9e2554a293..51fa2fbcaf325 100644
--- a/packages/gatsby-plugin-sass/src/__tests__/gatsby-node.js
+++ b/packages/gatsby-plugin-sass/src/__tests__/gatsby-node.js
@@ -73,6 +73,7 @@ describe(`pluginOptionsSchema`, () => {
   it(`should provide meaningful errors when fields are invalid`, async () => {
     const expectedErrors = [
       `"implementation" must be of type object`,
+      `"additionalData" must be one of [string, object]`,
       `"cssLoaderOptions" must be of type object`,
       `"postCssPlugins" must be an array`,
       `"sassRuleTest" must be of type object`,
@@ -99,6 +100,7 @@ describe(`pluginOptionsSchema`, () => {
     ]
 
     const { errors } = await testPluginOptionsSchema(pluginOptionsSchema, {
+      additionalData: 123,
       implementation: `This should be a require() thing`,
       postCssPlugins: `This should be an array of postCss plugins`,
       cssLoaderOptions: `This should be an object of css-loader options`,
@@ -132,6 +134,7 @@ describe(`pluginOptionsSchema`, () => {
 
   it(`should validate the schema`, async () => {
     const { isValid } = await testPluginOptionsSchema(pluginOptionsSchema, {
+      additionalData: `$test: #000;`,
       implementation: require(`../gatsby-node.js`),
       cssLoaderOptions: { camelCase: false },
       postCssPlugins: [require(`autoprefixer`)],
diff --git a/packages/gatsby-plugin-sass/src/gatsby-node.js b/packages/gatsby-plugin-sass/src/gatsby-node.js
index dc8bd2f05be7b..e752aca9e11e9 100644
--- a/packages/gatsby-plugin-sass/src/gatsby-node.js
+++ b/packages/gatsby-plugin-sass/src/gatsby-node.js
@@ -11,6 +11,7 @@ exports.onCreateWebpackConfig = (
     sassOptions = {},
     // eslint-disable-next-line no-unused-vars
     plugins,
+    additionalData = undefined,
     ...sassLoaderOptions
   }
 ) => {
@@ -22,6 +23,7 @@ exports.onCreateWebpackConfig = (
     options: {
       sourceMap: useResolveUrlLoader ? true : undefined,
       sassOptions,
+      additionalData,
       ...sassLoaderOptions,
     },
   }
@@ -94,6 +96,11 @@ exports.pluginOptionsSchema = function ({ Joi }) {
       .description(
         `By default the node implementation of Sass (node-sass) is used. To use the implementation written in Dart (dart-sass), you can install sass instead of node-sass and pass it into the options as the implementation`
       ),
+    additionalData: Joi.alternatives()
+      .try(Joi.string(), Joi.function())
+      .description(
+        `Prepends Sass/SCSS code before the actual entry file. In this case, the sass-loader will not override the data option but just prepend the entry's content. Learn more at: https://webpack.js.org/loaders/sass-loader/#additionaldata`
+      ),
     cssLoaderOptions: Joi.object({})
       .unknown(true)
       .description(