diff --git a/backend/src/langs.ts b/backend/src/langs.ts
index dc16b32..fe6a85b 100644
--- a/backend/src/langs.ts
+++ b/backend/src/langs.ts
@@ -562,6 +562,9 @@ int main() {
 }
 `,
     },
+    lsp: {
+      start: "/opt/omnisharp/run -lsp",
+    },
     template: `class main {
     static void Main(string[] args) {
         System.Console.WriteLine("Hello, world!");
diff --git a/scripts/docker-install-phase4.bash b/scripts/docker-install-phase4.bash
index bfed8f2..e65ecc6 100755
--- a/scripts/docker-install-phase4.bash
+++ b/scripts/docker-install-phase4.bash
@@ -39,6 +39,12 @@ wget -nv "ftp://ftp.gnu.org/gnu/apl/${file}"
 dpkg -i apl_*_amd64.deb
 rm apl_*_amd64.deb
 
+# C#
+wget -nv https://github.com/OmniSharp/omnisharp-roslyn/releases/download/v1.35.3/omnisharp-linux-x64.tar.gz
+mkdir /opt/omnisharp
+tar -xf omnisharp-linux-x64.tar.gz -C /opt/omnisharp
+rm omnisharp-linux-x64.tar.gz
+
 # Clojure
 ver="$(latest_release snoe/clojure-lsp)"
 wget -nv "https://github.com/snoe/clojure-lsp/releases/download/${ver}/clojure-lsp"