diff --git a/proto-gen/CHANGELOG.md b/proto-gen/CHANGELOG.md
index 86721e7..173b1ce 100644
--- a/proto-gen/CHANGELOG.md
+++ b/proto-gen/CHANGELOG.md
@@ -9,6 +9,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 <!-- next-header -->
 ## [Unreleased] - ReleaseDate
+### Added
+- [PR#24](https://github.com/EmbarkStudios/proto-gen/pull/24) Added `--btree-map` option to output BTreeMaps instead of HashMaps.
+
 ## [0.2.6] - 2024-04-25
 ### Added
 - [PR#23](https://github.com/EmbarkStudios/proto-gen/pull/23) Added `--enum-attribute` option to set enum attributes.
diff --git a/proto-gen/src/main.rs b/proto-gen/src/main.rs
index c87bd3e..08cdb9c 100644
--- a/proto-gen/src/main.rs
+++ b/proto-gen/src/main.rs
@@ -49,7 +49,7 @@ struct TonicOpts {
     #[clap(short = 'c', long)]
     build_client: bool,
 
-    /// Whether to generate the ::connect and similar functions for tonic.
+    /// Whether to generate the `::connect` and similar functions for tonic.
     #[clap(long)]
     generate_transport: bool,
 
@@ -57,6 +57,10 @@ struct TonicOpts {
     #[clap(short, long)]
     disable_comments: Vec<String>,
 
+    /// Output maps as `BTreeMap` instead of `HashMap`. Passing '.' makes all maps `BTreeMap`.
+    #[clap(short, long = "btree-map")]
+    btree_maps: Vec<String>,
+
     /// Type attributes to add.
     #[clap(long = "type-attribute", value_parser=KvValueParser)]
     type_attributes: Vec<(String, String)>,
@@ -144,6 +148,8 @@ fn run_with_opts(opts: Opts) -> Result<(), i32> {
     let mut config = prost_build::Config::new();
     config.disable_comments(opts.tonic.disable_comments);
 
+    config.btree_map(opts.tonic.btree_maps);
+
     let (ws, commit) = match opts.routine {
         Routine::Validate { workspace } => (workspace, false),
         Routine::Generate { workspace } => (workspace, true),
@@ -241,6 +247,7 @@ message TestMessage {
             disable_comments: vec![],
             type_attributes: vec![],
             enum_attributes: vec![],
+            btree_maps: vec![],
             client_attributes: vec![],
             server_attributes: vec![],
         };
@@ -389,6 +396,7 @@ message NestedTransitiveMsg {
             disable_comments: vec![],
             type_attributes: vec![],
             enum_attributes: vec![],
+            btree_maps: vec![],
             client_attributes: vec![],
             server_attributes: vec![],
         };