diff --git a/CHANGES.md b/CHANGES.md
index edbddcf9f..52c82514e 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -6,6 +6,11 @@
 
 # 1.23.1
 
+## Features
+
+- Add support for `.mlx` files, including formatting via `ocamlformat-mlx` and
+  most OCaml LSP features (diagnostics, code actions, hover, etc.) (#1528)
+
 ## Fixes
 
 - Fix hover on method calls not showing the type. (#1553, fixes #1552)
diff --git a/ocaml-lsp-server/src/code_actions.ml b/ocaml-lsp-server/src/code_actions.ml
index 662599eea..c2f7b9060 100644
--- a/ocaml-lsp-server/src/code_actions.ml
+++ b/ocaml-lsp-server/src/code_actions.ml
@@ -125,7 +125,7 @@ let compute server (params : CodeActionParams.t) =
     (match Document.syntax doc with
      | Ocamllex | Menhir | Cram | Dune ->
        Fiber.return (Reply.now (actions (dune_actions @ open_related)), state)
-     | Ocaml | Reason ->
+     | Ocaml | Reason | Mlx ->
        let reply () =
          let+ code_action_results = compute_ocaml_code_actions params state doc in
          List.concat [ code_action_results; dune_actions; open_related; merlin_jumps ]
diff --git a/ocaml-lsp-server/src/document.ml b/ocaml-lsp-server/src/document.ml
index fdee76287..213de261a 100644
--- a/ocaml-lsp-server/src/document.ml
+++ b/ocaml-lsp-server/src/document.ml
@@ -8,7 +8,7 @@ module Kind = struct
 
   let of_fname_opt p =
     match Filename.extension p with
-    | ".ml" | ".eliom" | ".re" | ".mll" | ".mly" -> Some Impl
+    | ".ml" | ".eliom" | ".re" | ".mll" | ".mly" | ".mlx" -> Some Impl
     | ".mli" | ".eliomi" | ".rei" -> Some Intf
     | _ -> None
   ;;
@@ -32,6 +32,7 @@ module Syntax = struct
     | Menhir
     | Cram
     | Dune
+    | Mlx
 
   let human_name = function
     | Ocaml -> "OCaml"
@@ -40,6 +41,7 @@ module Syntax = struct
     | Menhir -> "Menhir/ocamlyacc"
     | Cram -> "Cram"
     | Dune -> "Dune"
+    | Mlx -> "OCaml.mlx"
   ;;
 
   let all =
@@ -52,6 +54,7 @@ module Syntax = struct
     ; "dune", Dune
     ; "dune-project", Dune
     ; "dune-workspace", Dune
+    ; "ocaml.mlx", Mlx
     ]
   ;;
 
@@ -61,6 +64,7 @@ module Syntax = struct
       | s ->
         (match Filename.extension s with
          | ".eliomi" | ".eliom" | ".mli" | ".ml" -> Ok Ocaml
+         | ".mlx" -> Ok Mlx
          | ".rei" | ".re" -> Ok Reason
          | ".mll" -> Ok Ocamllex
          | ".mly" -> Ok Menhir
@@ -252,7 +256,7 @@ let make wheel config pipeline (doc : DidOpenTextDocumentParams.t) ~position_enc
     let tdoc = Text_document.make ~position_encoding doc in
     let syntax = Syntax.of_text_document tdoc in
     match syntax with
-    | Ocaml | Reason -> make_merlin wheel config pipeline tdoc syntax
+    | Ocaml | Reason | Mlx -> make_merlin wheel config pipeline tdoc syntax
     | Ocamllex | Menhir | Cram | Dune -> Fiber.return (Other { tdoc; syntax }))
 ;;
 
@@ -421,8 +425,8 @@ let close t =
 let get_impl_intf_counterparts m uri =
   let fpath = Uri.to_path uri in
   let fname = Filename.basename fpath in
-  let ml, mli, eliom, eliomi, re, rei, mll, mly =
-    "ml", "mli", "eliom", "eliomi", "re", "rei", "mll", "mly"
+  let ml, mli, eliom, eliomi, re, rei, mll, mly, mlx =
+    "ml", "mli", "eliom", "eliomi", "re", "rei", "mll", "mly", "mlx"
   in
   let exts_to_switch_to =
     let kind =
@@ -436,13 +440,17 @@ let get_impl_intf_counterparts m uri =
     in
     match Syntax.of_fname fname with
     | Dune | Cram -> []
+    | Mlx ->
+      (match kind with
+       | Intf -> [ ml; mly; mll; mlx; re ]
+       | Impl -> [ rei; mli; mly; mll; rei ])
     | Ocaml ->
       (match kind with
-       | Intf -> [ ml; mly; mll; eliom; re ]
+       | Intf -> [ ml; mly; mll; eliom; re; mlx ]
        | Impl -> [ mli; mly; mll; eliomi; rei ])
     | Reason ->
       (match kind with
-       | Intf -> [ re; ml ]
+       | Intf -> [ re; ml; mlx ]
        | Impl -> [ rei; mli ])
     | Ocamllex -> [ mli; rei ]
     | Menhir -> [ mli; rei ]
diff --git a/ocaml-lsp-server/src/document.mli b/ocaml-lsp-server/src/document.mli
index 735bfd659..6585b6f0b 100644
--- a/ocaml-lsp-server/src/document.mli
+++ b/ocaml-lsp-server/src/document.mli
@@ -10,6 +10,7 @@ module Syntax : sig
     | Menhir
     | Cram
     | Dune
+    | Mlx
 
   val human_name : t -> string
   val markdown_name : t -> string
diff --git a/ocaml-lsp-server/src/inference.ml b/ocaml-lsp-server/src/inference.ml
index d51401e31..c313b7bd2 100644
--- a/ocaml-lsp-server/src/inference.ml
+++ b/ocaml-lsp-server/src/inference.ml
@@ -71,6 +71,7 @@ let language_id_of_fname s =
   | ".mli" | ".eliomi" -> "ocaml.interface"
   | ".ml" | ".eliom" -> "ocaml"
   | ".rei" | ".re" -> "reason"
+  | ".mlx" -> "ocaml.mlx"
   | ".mll" -> "ocaml.ocamllex"
   | ".mly" -> "ocaml.menhir"
   | ext -> Code_error.raise "unsupported file extension" [ "extension", String ext ]
diff --git a/ocaml-lsp-server/src/ocaml_lsp_server.ml b/ocaml-lsp-server/src/ocaml_lsp_server.ml
index ec7f8e119..39e58db09 100644
--- a/ocaml-lsp-server/src/ocaml_lsp_server.ml
+++ b/ocaml-lsp-server/src/ocaml_lsp_server.ml
@@ -203,7 +203,7 @@ let set_diagnostics detached diagnostics doc =
        in
        Diagnostics.set diagnostics (`Merlin (uri, [ no_reason_merlin ]));
        async (fun () -> Diagnostics.send diagnostics (`One uri))
-     | Reason | Ocaml ->
+     | Reason | Ocaml | Mlx ->
        async (fun () ->
          let* () = Diagnostics.merlin_diagnostics diagnostics merlin in
          Diagnostics.send diagnostics (`One uri)))
diff --git a/ocaml-lsp-server/src/ocamlformat.ml b/ocaml-lsp-server/src/ocamlformat.ml
index 28437f21f..4c6ce3757 100644
--- a/ocaml-lsp-server/src/ocamlformat.ml
+++ b/ocaml-lsp-server/src/ocamlformat.ml
@@ -100,9 +100,11 @@ let message = function
 type formatter =
   | Reason of Document.Kind.t
   | Ocaml of Uri.t
+  | Mlx of Uri.t
 
 let args = function
   | Ocaml uri -> [ sprintf "--name=%s" (Uri.to_path uri); "-" ]
+  | Mlx uri -> [ "--impl"; sprintf "--name=%s" (Uri.to_path uri); "-" ]
   | Reason kind ->
     [ "--parse"; "re"; "--print"; "re" ]
     @
@@ -114,6 +116,7 @@ let args = function
 let binary_name t =
   match t with
   | Ocaml _ -> "ocamlformat"
+  | Mlx _ -> "ocamlformat-mlx"
   | Reason _ -> "refmt"
 ;;
 
@@ -128,6 +131,7 @@ let formatter doc =
   match Document.syntax doc with
   | (Dune | Cram | Ocamllex | Menhir) as s -> Error (Unsupported_syntax s)
   | Ocaml -> Ok (Ocaml (Document.uri doc))
+  | Mlx -> Ok (Mlx (Document.uri doc))
   | Reason ->
     Ok
       (Reason
diff --git a/ocaml-lsp-server/src/ocamlformat.mli b/ocaml-lsp-server/src/ocamlformat.mli
index 0d6edc6c1..186f692ba 100644
--- a/ocaml-lsp-server/src/ocamlformat.mli
+++ b/ocaml-lsp-server/src/ocamlformat.mli
@@ -1,6 +1,7 @@
 (** Generic formatting facility for OCaml and Reason sources.
 
-    Relies on [ocamlformat] for OCaml and [refmt] for reason *)
+    Relies on [ocamlformat] for OCaml, [ocamlformat-mlx] for OCaml.mlx, and
+    [refmt] for Reason. *)
 
 open Import