diff --git a/README.md b/README.md
index 3cf25ab2d..c60c133fd 100644
--- a/README.md
+++ b/README.md
@@ -75,6 +75,7 @@
   - [Dates](#dates)
   - [Times](#times)
   - [IP addresses](#ip-addresses)
+  - [IP ranges](#ip-ranges-cidr)
 - [Numbers](#numbers)
 - [BigInts](#bigints)
 - [NaNs](#nans)
@@ -777,6 +778,7 @@ z.string().startsWith(string);
 z.string().endsWith(string);
 z.string().datetime(); // ISO 8601; by default only `Z` timezone allowed
 z.string().ip(); // defaults to allow both IPv4 and IPv6
+z.string().cidr(); // defaults to allow both IPv4 and IPv6
 
 // transforms
 z.string().trim(); // trim whitespace
@@ -818,6 +820,7 @@ z.string().datetime({ message: "Invalid datetime string! Must be UTC." });
 z.string().date({ message: "Invalid date string!" });
 z.string().time({ message: "Invalid time string!" });
 z.string().ip({ message: "Invalid IP address" });
+z.string().cidr({ message: "Invalid CIDR" });
 ```
 
 ### Datetimes
@@ -900,7 +903,7 @@ time.parse("00:00:00"); // fail
 
 ### IP addresses
 
-The `z.string().ip()` method by default validate IPv4 and IPv6.
+By default `.ip()` allows both IPv4 and IPv6.
 
 ```ts
 const ip = z.string().ip();
@@ -923,6 +926,26 @@ const ipv6 = z.string().ip({ version: "v6" });
 ipv6.parse("192.168.1.1"); // fail
 ```
 
+### IP ranges (CIDR)
+
+Validate IP address ranges specified with [CIDR notation](https://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing). By default, `.cidr()` allows both IPv4 and IPv6.
+
+```ts
+const cidr = z.string().cidr();
+cidr.parse("192.168.0.0/24"); // pass
+cidr.parse("2001:db8::/32"); // pass
+```
+
+You can specify a version with the `version` parameter.
+
+```ts
+const ipv4Cidr = z.string().cidr({ version: "v4" });
+ipv4Cidr.parse("84d5:51a0:9114:1855:4cfa:f2d7:1f12:7003"); // fail
+
+const ipv6Cidr = z.string().cidr({ version: "v6" });
+ipv6Cidr.parse("192.168.1.1"); // fail
+```
+
 ## Numbers
 
 You can customize certain error messages when creating a number schema.
diff --git a/deno/lib/README.md b/deno/lib/README.md
index a3c888695..2f5af57c2 100644
--- a/deno/lib/README.md
+++ b/deno/lib/README.md
@@ -76,6 +76,7 @@
   - [Dates](#dates)
   - [Times](#times)
   - [IP addresses](#ip-addresses)
+  - [IP ranges](#ip-ranges-cidr)
 - [Numbers](#numbers)
 - [BigInts](#bigints)
 - [NaNs](#nans)
@@ -787,6 +788,7 @@ z.string().startsWith(string);
 z.string().endsWith(string);
 z.string().datetime(); // ISO 8601; by default only `Z` timezone allowed
 z.string().ip(); // defaults to allow both IPv4 and IPv6
+z.string().cidr(); // defaults to allow both IPv4 and IPv6
 
 // transforms
 z.string().trim(); // trim whitespace
@@ -828,6 +830,7 @@ z.string().datetime({ message: "Invalid datetime string! Must be UTC." });
 z.string().date({ message: "Invalid date string!" });
 z.string().time({ message: "Invalid time string!" });
 z.string().ip({ message: "Invalid IP address" });
+z.string().cidr({ message: "Invalid CIDR" });
 ```
 
 ### Datetimes
@@ -910,7 +913,7 @@ time.parse("00:00:00"); // fail
 
 ### IP addresses
 
-The `z.string().ip()` method by default validate IPv4 and IPv6.
+By default `.ip()` allows both IPv4 and IPv6.
 
 ```ts
 const ip = z.string().ip();
@@ -933,6 +936,26 @@ const ipv6 = z.string().ip({ version: "v6" });
 ipv6.parse("192.168.1.1"); // fail
 ```
 
+### IP ranges (CIDR)
+
+Validate IP address ranges specified with [CIDR notation](https://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing). By default, `.cidr()` allows both IPv4 and IPv6.
+
+```ts
+const cidr = z.string().cidr();
+cidr.parse("192.168.0.0/24"); // pass
+cidr.parse("2001:db8::/32"); // pass
+```
+
+You can specify a version with the `version` parameter.
+
+```ts
+const ipv4Cidr = z.string().cidr({ version: "v4" });
+ipv4Cidr.parse("84d5:51a0:9114:1855:4cfa:f2d7:1f12:7003"); // fail
+
+const ipv6Cidr = z.string().cidr({ version: "v6" });
+ipv6Cidr.parse("192.168.1.1"); // fail
+```
+
 ## Numbers
 
 You can customize certain error messages when creating a number schema.
diff --git a/deno/lib/ZodError.ts b/deno/lib/ZodError.ts
index e757cd8ba..21ad657a3 100644
--- a/deno/lib/ZodError.ts
+++ b/deno/lib/ZodError.ts
@@ -103,6 +103,7 @@ export type StringValidation =
   | "time"
   | "duration"
   | "ip"
+  | "cidr"
   | "base64"
   | { includes: string; position?: number }
   | { startsWith: string }
diff --git a/deno/lib/__tests__/string.test.ts b/deno/lib/__tests__/string.test.ts
index 64438717a..3c059f0b0 100644
--- a/deno/lib/__tests__/string.test.ts
+++ b/deno/lib/__tests__/string.test.ts
@@ -373,6 +373,7 @@ test("checks getters", () => {
   expect(z.string().email().isUUID).toEqual(false);
   expect(z.string().email().isNANOID).toEqual(false);
   expect(z.string().email().isIP).toEqual(false);
+  expect(z.string().email().isCIDR).toEqual(false);
   expect(z.string().email().isULID).toEqual(false);
 
   expect(z.string().url().isEmail).toEqual(false);
@@ -382,6 +383,7 @@ test("checks getters", () => {
   expect(z.string().url().isUUID).toEqual(false);
   expect(z.string().url().isNANOID).toEqual(false);
   expect(z.string().url().isIP).toEqual(false);
+  expect(z.string().url().isCIDR).toEqual(false);
   expect(z.string().url().isULID).toEqual(false);
 
   expect(z.string().cuid().isEmail).toEqual(false);
@@ -391,6 +393,7 @@ test("checks getters", () => {
   expect(z.string().cuid().isUUID).toEqual(false);
   expect(z.string().cuid().isNANOID).toEqual(false);
   expect(z.string().cuid().isIP).toEqual(false);
+  expect(z.string().cuid().isCIDR).toEqual(false);
   expect(z.string().cuid().isULID).toEqual(false);
 
   expect(z.string().cuid2().isEmail).toEqual(false);
@@ -400,6 +403,7 @@ test("checks getters", () => {
   expect(z.string().cuid2().isUUID).toEqual(false);
   expect(z.string().cuid2().isNANOID).toEqual(false);
   expect(z.string().cuid2().isIP).toEqual(false);
+  expect(z.string().cuid2().isCIDR).toEqual(false);
   expect(z.string().cuid2().isULID).toEqual(false);
 
   expect(z.string().uuid().isEmail).toEqual(false);
@@ -409,6 +413,7 @@ test("checks getters", () => {
   expect(z.string().uuid().isUUID).toEqual(true);
   expect(z.string().uuid().isNANOID).toEqual(false);
   expect(z.string().uuid().isIP).toEqual(false);
+  expect(z.string().uuid().isCIDR).toEqual(false);
   expect(z.string().uuid().isULID).toEqual(false);
 
   expect(z.string().nanoid().isEmail).toEqual(false);
@@ -418,6 +423,7 @@ test("checks getters", () => {
   expect(z.string().nanoid().isUUID).toEqual(false);
   expect(z.string().nanoid().isNANOID).toEqual(true);
   expect(z.string().nanoid().isIP).toEqual(false);
+  expect(z.string().nanoid().isCIDR).toEqual(false);
   expect(z.string().nanoid().isULID).toEqual(false);
 
   expect(z.string().ip().isEmail).toEqual(false);
@@ -427,8 +433,19 @@ test("checks getters", () => {
   expect(z.string().ip().isUUID).toEqual(false);
   expect(z.string().ip().isNANOID).toEqual(false);
   expect(z.string().ip().isIP).toEqual(true);
+  expect(z.string().ip().isCIDR).toEqual(false);
   expect(z.string().ip().isULID).toEqual(false);
 
+  expect(z.string().cidr().isEmail).toEqual(false);
+  expect(z.string().cidr().isURL).toEqual(false);
+  expect(z.string().cidr().isCUID).toEqual(false);
+  expect(z.string().cidr().isCUID2).toEqual(false);
+  expect(z.string().cidr().isUUID).toEqual(false);
+  expect(z.string().cidr().isNANOID).toEqual(false);
+  expect(z.string().cidr().isIP).toEqual(false);
+  expect(z.string().cidr().isCIDR).toEqual(true);
+  expect(z.string().cidr().isULID).toEqual(false);
+
   expect(z.string().ulid().isEmail).toEqual(false);
   expect(z.string().ulid().isURL).toEqual(false);
   expect(z.string().ulid().isCUID).toEqual(false);
@@ -436,6 +453,7 @@ test("checks getters", () => {
   expect(z.string().ulid().isUUID).toEqual(false);
   expect(z.string().ulid().isNANOID).toEqual(false);
   expect(z.string().ulid().isIP).toEqual(false);
+  expect(z.string().ulid().isCIDR).toEqual(false);
   expect(z.string().ulid().isULID).toEqual(true);
 });
 
@@ -769,3 +787,45 @@ test("IP validation", () => {
     invalidIPs.every((ip) => ipSchema.safeParse(ip).success === false)
   ).toBe(true);
 });
+
+test("CIDR validation", () => {
+  const ipv4Cidr = z.string().cidr({ version: "v4" });
+  expect(() => ipv4Cidr.parse("2001:0db8:85a3::8a2e:0370:7334/64")).toThrow();
+
+  const ipv6Cidr = z.string().cidr({ version: "v6" });
+  expect(() => ipv6Cidr.parse("192.168.0.1/24")).toThrow();
+
+  const validCidrs = [
+    "192.168.0.0/24",
+    "10.0.0.0/8",
+    "203.0.113.0/24",
+    "192.0.2.0/24",
+    "127.0.0.0/8",
+    "172.16.0.0/12",
+    "192.168.1.0/24",
+    "fc00::/7",
+    "fd00::/8",
+    "2001:db8::/32",
+    "2607:f0d0:1002:51::4/64",
+    "2001:0db8:85a3:0000:0000:8a2e:0370:7334/128",
+    "2001:0db8:1234:0000::/64",
+  ];
+
+  const invalidCidrs = [
+    "192.168.1.1/33",
+    "10.0.0.1/-1",
+    "192.168.1.1/24/24",
+    "192.168.1.0/abc",
+    "2001:db8::1/129",
+    "2001:db8::1/-1",
+    "2001:db8::1/64/64",
+    "2001:db8::1/abc",
+  ];
+
+  // no parameters check IPv4 or IPv6
+  const cidrSchema = z.string().cidr();
+  expect(validCidrs.every((ip) => cidrSchema.safeParse(ip).success)).toBe(true);
+  expect(
+    invalidCidrs.every((ip) => cidrSchema.safeParse(ip).success === false)
+  ).toBe(true);
+});
diff --git a/deno/lib/types.ts b/deno/lib/types.ts
index 9cee39a35..42d2606bb 100644
--- a/deno/lib/types.ts
+++ b/deno/lib/types.ts
@@ -565,6 +565,7 @@ export type ZodStringCheck =
     }
   | { kind: "duration"; message?: string }
   | { kind: "ip"; version?: IpVersion; message?: string }
+  | { kind: "cidr"; version?: IpVersion; message?: string }
   | { kind: "base64"; message?: string };
 
 export interface ZodStringDef extends ZodTypeDef {
@@ -608,11 +609,15 @@ let emojiRegex: RegExp;
 // faster, simpler, safer
 const ipv4Regex =
   /^(?:(?:25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9][0-9]|[0-9])\.){3}(?:25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9][0-9]|[0-9])$/;
+const ipv4CidrRegex =
+  /^(?:(?:25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9][0-9]|[0-9])\.){3}(?:25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9][0-9]|[0-9])\/(3[0-2]|[12]?[0-9])$/;
 
 // const ipv6Regex =
 // /^(([a-f0-9]{1,4}:){7}|::([a-f0-9]{1,4}:){0,6}|([a-f0-9]{1,4}:){1}:([a-f0-9]{1,4}:){0,5}|([a-f0-9]{1,4}:){2}:([a-f0-9]{1,4}:){0,4}|([a-f0-9]{1,4}:){3}:([a-f0-9]{1,4}:){0,3}|([a-f0-9]{1,4}:){4}:([a-f0-9]{1,4}:){0,2}|([a-f0-9]{1,4}:){5}:([a-f0-9]{1,4}:){0,1})([a-f0-9]{1,4}|(((25[0-5])|(2[0-4][0-9])|(1[0-9]{2})|([0-9]{1,2}))\.){3}((25[0-5])|(2[0-4][0-9])|(1[0-9]{2})|([0-9]{1,2})))$/;
 const ipv6Regex =
   /^(([0-9a-fA-F]{1,4}:){7,7}[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,7}:|([0-9a-fA-F]{1,4}:){1,6}:[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,5}(:[0-9a-fA-F]{1,4}){1,2}|([0-9a-fA-F]{1,4}:){1,4}(:[0-9a-fA-F]{1,4}){1,3}|([0-9a-fA-F]{1,4}:){1,3}(:[0-9a-fA-F]{1,4}){1,4}|([0-9a-fA-F]{1,4}:){1,2}(:[0-9a-fA-F]{1,4}){1,5}|[0-9a-fA-F]{1,4}:((:[0-9a-fA-F]{1,4}){1,6})|:((:[0-9a-fA-F]{1,4}){1,7}|:)|fe80:(:[0-9a-fA-F]{0,4}){0,4}%[0-9a-zA-Z]{1,}|::(ffff(:0{1,4}){0,1}:){0,1}((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])|([0-9a-fA-F]{1,4}:){1,4}:((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9]))$/;
+const ipv6CidrRegex =
+  /^(([0-9a-fA-F]{1,4}:){7,7}[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,7}:|([0-9a-fA-F]{1,4}:){1,6}:[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,5}(:[0-9a-fA-F]{1,4}){1,2}|([0-9a-fA-F]{1,4}:){1,4}(:[0-9a-fA-F]{1,4}){1,3}|([0-9a-fA-F]{1,4}:){1,3}(:[0-9a-fA-F]{1,4}){1,4}|([0-9a-fA-F]{1,4}:){1,2}(:[0-9a-fA-F]{1,4}){1,5}|[0-9a-fA-F]{1,4}:((:[0-9a-fA-F]{1,4}){1,6})|:((:[0-9a-fA-F]{1,4}){1,7}|:)|fe80:(:[0-9a-fA-F]{0,4}){0,4}%[0-9a-zA-Z]{1,}|::(ffff(:0{1,4}){0,1}:){0,1}((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])|([0-9a-fA-F]{1,4}:){1,4}:((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9]))\/(12[0-8]|1[01][0-9]|[1-9]?[0-9])$/;
 
 // https://stackoverflow.com/questions/7860392/determine-if-string-is-in-base64-using-javascript
 const base64Regex =
@@ -671,6 +676,17 @@ function isValidIP(ip: string, version?: IpVersion) {
   return false;
 }
 
+function isValidCidr(ip: string, version?: IpVersion) {
+  if ((version === "v4" || !version) && ipv4CidrRegex.test(ip)) {
+    return true;
+  }
+  if ((version === "v6" || !version) && ipv6CidrRegex.test(ip)) {
+    return true;
+  }
+
+  return false;
+}
+
 export class ZodString extends ZodType<string, ZodStringDef, string> {
   _parse(input: ParseInput): ParseReturnType<string> {
     if (this._def.coerce) {
@@ -933,6 +949,16 @@ export class ZodString extends ZodType<string, ZodStringDef, string> {
           });
           status.dirty();
         }
+      } else if (check.kind === "cidr") {
+        if (!isValidCidr(input.data, check.version)) {
+          ctx = this._getOrReturnCtx(input, ctx);
+          addIssueToContext(ctx, {
+            validation: "cidr",
+            code: ZodIssueCode.invalid_string,
+            message: check.message,
+          });
+          status.dirty();
+        }
       } else if (check.kind === "base64") {
         if (!base64Regex.test(input.data)) {
           ctx = this._getOrReturnCtx(input, ctx);
@@ -1006,6 +1032,10 @@ export class ZodString extends ZodType<string, ZodStringDef, string> {
     return this._addCheck({ kind: "ip", ...errorUtil.errToObj(options) });
   }
 
+  cidr(options?: string | { version?: IpVersion; message?: string }) {
+    return this._addCheck({ kind: "cidr", ...errorUtil.errToObj(options) });
+  }
+
   datetime(
     options?:
       | string
@@ -1199,6 +1229,9 @@ export class ZodString extends ZodType<string, ZodStringDef, string> {
   get isIP() {
     return !!this._def.checks.find((ch) => ch.kind === "ip");
   }
+  get isCIDR() {
+    return !!this._def.checks.find((ch) => ch.kind === "cidr");
+  }
   get isBase64() {
     return !!this._def.checks.find((ch) => ch.kind === "base64");
   }
diff --git a/src/ZodError.ts b/src/ZodError.ts
index c1f7aa3ee..6e0da79dc 100644
--- a/src/ZodError.ts
+++ b/src/ZodError.ts
@@ -103,6 +103,7 @@ export type StringValidation =
   | "time"
   | "duration"
   | "ip"
+  | "cidr"
   | "base64"
   | { includes: string; position?: number }
   | { startsWith: string }
diff --git a/src/__tests__/string.test.ts b/src/__tests__/string.test.ts
index f7037fcc2..ef5190062 100644
--- a/src/__tests__/string.test.ts
+++ b/src/__tests__/string.test.ts
@@ -372,6 +372,7 @@ test("checks getters", () => {
   expect(z.string().email().isUUID).toEqual(false);
   expect(z.string().email().isNANOID).toEqual(false);
   expect(z.string().email().isIP).toEqual(false);
+  expect(z.string().email().isCIDR).toEqual(false);
   expect(z.string().email().isULID).toEqual(false);
 
   expect(z.string().url().isEmail).toEqual(false);
@@ -381,6 +382,7 @@ test("checks getters", () => {
   expect(z.string().url().isUUID).toEqual(false);
   expect(z.string().url().isNANOID).toEqual(false);
   expect(z.string().url().isIP).toEqual(false);
+  expect(z.string().url().isCIDR).toEqual(false);
   expect(z.string().url().isULID).toEqual(false);
 
   expect(z.string().cuid().isEmail).toEqual(false);
@@ -390,6 +392,7 @@ test("checks getters", () => {
   expect(z.string().cuid().isUUID).toEqual(false);
   expect(z.string().cuid().isNANOID).toEqual(false);
   expect(z.string().cuid().isIP).toEqual(false);
+  expect(z.string().cuid().isCIDR).toEqual(false);
   expect(z.string().cuid().isULID).toEqual(false);
 
   expect(z.string().cuid2().isEmail).toEqual(false);
@@ -399,6 +402,7 @@ test("checks getters", () => {
   expect(z.string().cuid2().isUUID).toEqual(false);
   expect(z.string().cuid2().isNANOID).toEqual(false);
   expect(z.string().cuid2().isIP).toEqual(false);
+  expect(z.string().cuid2().isCIDR).toEqual(false);
   expect(z.string().cuid2().isULID).toEqual(false);
 
   expect(z.string().uuid().isEmail).toEqual(false);
@@ -408,6 +412,7 @@ test("checks getters", () => {
   expect(z.string().uuid().isUUID).toEqual(true);
   expect(z.string().uuid().isNANOID).toEqual(false);
   expect(z.string().uuid().isIP).toEqual(false);
+  expect(z.string().uuid().isCIDR).toEqual(false);
   expect(z.string().uuid().isULID).toEqual(false);
 
   expect(z.string().nanoid().isEmail).toEqual(false);
@@ -417,6 +422,7 @@ test("checks getters", () => {
   expect(z.string().nanoid().isUUID).toEqual(false);
   expect(z.string().nanoid().isNANOID).toEqual(true);
   expect(z.string().nanoid().isIP).toEqual(false);
+  expect(z.string().nanoid().isCIDR).toEqual(false);
   expect(z.string().nanoid().isULID).toEqual(false);
 
   expect(z.string().ip().isEmail).toEqual(false);
@@ -426,8 +432,19 @@ test("checks getters", () => {
   expect(z.string().ip().isUUID).toEqual(false);
   expect(z.string().ip().isNANOID).toEqual(false);
   expect(z.string().ip().isIP).toEqual(true);
+  expect(z.string().ip().isCIDR).toEqual(false);
   expect(z.string().ip().isULID).toEqual(false);
 
+  expect(z.string().cidr().isEmail).toEqual(false);
+  expect(z.string().cidr().isURL).toEqual(false);
+  expect(z.string().cidr().isCUID).toEqual(false);
+  expect(z.string().cidr().isCUID2).toEqual(false);
+  expect(z.string().cidr().isUUID).toEqual(false);
+  expect(z.string().cidr().isNANOID).toEqual(false);
+  expect(z.string().cidr().isIP).toEqual(false);
+  expect(z.string().cidr().isCIDR).toEqual(true);
+  expect(z.string().cidr().isULID).toEqual(false);
+
   expect(z.string().ulid().isEmail).toEqual(false);
   expect(z.string().ulid().isURL).toEqual(false);
   expect(z.string().ulid().isCUID).toEqual(false);
@@ -435,6 +452,7 @@ test("checks getters", () => {
   expect(z.string().ulid().isUUID).toEqual(false);
   expect(z.string().ulid().isNANOID).toEqual(false);
   expect(z.string().ulid().isIP).toEqual(false);
+  expect(z.string().ulid().isCIDR).toEqual(false);
   expect(z.string().ulid().isULID).toEqual(true);
 });
 
@@ -768,3 +786,45 @@ test("IP validation", () => {
     invalidIPs.every((ip) => ipSchema.safeParse(ip).success === false)
   ).toBe(true);
 });
+
+test("CIDR validation", () => {
+  const ipv4Cidr = z.string().cidr({ version: "v4" });
+  expect(() => ipv4Cidr.parse("2001:0db8:85a3::8a2e:0370:7334/64")).toThrow();
+
+  const ipv6Cidr = z.string().cidr({ version: "v6" });
+  expect(() => ipv6Cidr.parse("192.168.0.1/24")).toThrow();
+
+  const validCidrs = [
+    "192.168.0.0/24",
+    "10.0.0.0/8",
+    "203.0.113.0/24",
+    "192.0.2.0/24",
+    "127.0.0.0/8",
+    "172.16.0.0/12",
+    "192.168.1.0/24",
+    "fc00::/7",
+    "fd00::/8",
+    "2001:db8::/32",
+    "2607:f0d0:1002:51::4/64",
+    "2001:0db8:85a3:0000:0000:8a2e:0370:7334/128",
+    "2001:0db8:1234:0000::/64",
+  ];
+
+  const invalidCidrs = [
+    "192.168.1.1/33",
+    "10.0.0.1/-1",
+    "192.168.1.1/24/24",
+    "192.168.1.0/abc",
+    "2001:db8::1/129",
+    "2001:db8::1/-1",
+    "2001:db8::1/64/64",
+    "2001:db8::1/abc",
+  ];
+
+  // no parameters check IPv4 or IPv6
+  const cidrSchema = z.string().cidr();
+  expect(validCidrs.every((ip) => cidrSchema.safeParse(ip).success)).toBe(true);
+  expect(
+    invalidCidrs.every((ip) => cidrSchema.safeParse(ip).success === false)
+  ).toBe(true);
+});
diff --git a/src/types.ts b/src/types.ts
index be49c7012..df298ae3f 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -565,6 +565,7 @@ export type ZodStringCheck =
     }
   | { kind: "duration"; message?: string }
   | { kind: "ip"; version?: IpVersion; message?: string }
+  | { kind: "cidr"; version?: IpVersion; message?: string }
   | { kind: "base64"; message?: string };
 
 export interface ZodStringDef extends ZodTypeDef {
@@ -608,11 +609,15 @@ let emojiRegex: RegExp;
 // faster, simpler, safer
 const ipv4Regex =
   /^(?:(?:25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9][0-9]|[0-9])\.){3}(?:25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9][0-9]|[0-9])$/;
+const ipv4CidrRegex =
+  /^(?:(?:25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9][0-9]|[0-9])\.){3}(?:25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9][0-9]|[0-9])\/(3[0-2]|[12]?[0-9])$/;
 
 // const ipv6Regex =
 // /^(([a-f0-9]{1,4}:){7}|::([a-f0-9]{1,4}:){0,6}|([a-f0-9]{1,4}:){1}:([a-f0-9]{1,4}:){0,5}|([a-f0-9]{1,4}:){2}:([a-f0-9]{1,4}:){0,4}|([a-f0-9]{1,4}:){3}:([a-f0-9]{1,4}:){0,3}|([a-f0-9]{1,4}:){4}:([a-f0-9]{1,4}:){0,2}|([a-f0-9]{1,4}:){5}:([a-f0-9]{1,4}:){0,1})([a-f0-9]{1,4}|(((25[0-5])|(2[0-4][0-9])|(1[0-9]{2})|([0-9]{1,2}))\.){3}((25[0-5])|(2[0-4][0-9])|(1[0-9]{2})|([0-9]{1,2})))$/;
 const ipv6Regex =
   /^(([0-9a-fA-F]{1,4}:){7,7}[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,7}:|([0-9a-fA-F]{1,4}:){1,6}:[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,5}(:[0-9a-fA-F]{1,4}){1,2}|([0-9a-fA-F]{1,4}:){1,4}(:[0-9a-fA-F]{1,4}){1,3}|([0-9a-fA-F]{1,4}:){1,3}(:[0-9a-fA-F]{1,4}){1,4}|([0-9a-fA-F]{1,4}:){1,2}(:[0-9a-fA-F]{1,4}){1,5}|[0-9a-fA-F]{1,4}:((:[0-9a-fA-F]{1,4}){1,6})|:((:[0-9a-fA-F]{1,4}){1,7}|:)|fe80:(:[0-9a-fA-F]{0,4}){0,4}%[0-9a-zA-Z]{1,}|::(ffff(:0{1,4}){0,1}:){0,1}((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])|([0-9a-fA-F]{1,4}:){1,4}:((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9]))$/;
+const ipv6CidrRegex =
+  /^(([0-9a-fA-F]{1,4}:){7,7}[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,7}:|([0-9a-fA-F]{1,4}:){1,6}:[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,5}(:[0-9a-fA-F]{1,4}){1,2}|([0-9a-fA-F]{1,4}:){1,4}(:[0-9a-fA-F]{1,4}){1,3}|([0-9a-fA-F]{1,4}:){1,3}(:[0-9a-fA-F]{1,4}){1,4}|([0-9a-fA-F]{1,4}:){1,2}(:[0-9a-fA-F]{1,4}){1,5}|[0-9a-fA-F]{1,4}:((:[0-9a-fA-F]{1,4}){1,6})|:((:[0-9a-fA-F]{1,4}){1,7}|:)|fe80:(:[0-9a-fA-F]{0,4}){0,4}%[0-9a-zA-Z]{1,}|::(ffff(:0{1,4}){0,1}:){0,1}((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])|([0-9a-fA-F]{1,4}:){1,4}:((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9]))\/(12[0-8]|1[01][0-9]|[1-9]?[0-9])$/;
 
 // https://stackoverflow.com/questions/7860392/determine-if-string-is-in-base64-using-javascript
 const base64Regex =
@@ -671,6 +676,17 @@ function isValidIP(ip: string, version?: IpVersion) {
   return false;
 }
 
+function isValidCidr(ip: string, version?: IpVersion) {
+  if ((version === "v4" || !version) && ipv4CidrRegex.test(ip)) {
+    return true;
+  }
+  if ((version === "v6" || !version) && ipv6CidrRegex.test(ip)) {
+    return true;
+  }
+
+  return false;
+}
+
 export class ZodString extends ZodType<string, ZodStringDef, string> {
   _parse(input: ParseInput): ParseReturnType<string> {
     if (this._def.coerce) {
@@ -933,6 +949,16 @@ export class ZodString extends ZodType<string, ZodStringDef, string> {
           });
           status.dirty();
         }
+      } else if (check.kind === "cidr") {
+        if (!isValidCidr(input.data, check.version)) {
+          ctx = this._getOrReturnCtx(input, ctx);
+          addIssueToContext(ctx, {
+            validation: "cidr",
+            code: ZodIssueCode.invalid_string,
+            message: check.message,
+          });
+          status.dirty();
+        }
       } else if (check.kind === "base64") {
         if (!base64Regex.test(input.data)) {
           ctx = this._getOrReturnCtx(input, ctx);
@@ -1006,6 +1032,10 @@ export class ZodString extends ZodType<string, ZodStringDef, string> {
     return this._addCheck({ kind: "ip", ...errorUtil.errToObj(options) });
   }
 
+  cidr(options?: string | { version?: IpVersion; message?: string }) {
+    return this._addCheck({ kind: "cidr", ...errorUtil.errToObj(options) });
+  }
+
   datetime(
     options?:
       | string
@@ -1199,6 +1229,9 @@ export class ZodString extends ZodType<string, ZodStringDef, string> {
   get isIP() {
     return !!this._def.checks.find((ch) => ch.kind === "ip");
   }
+  get isCIDR() {
+    return !!this._def.checks.find((ch) => ch.kind === "cidr");
+  }
   get isBase64() {
     return !!this._def.checks.find((ch) => ch.kind === "base64");
   }