diff --git a/.gitmodules b/.gitmodules
index 664c7d85e..3befa39e8 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -5,3 +5,6 @@
 	path = lib/rain.interpreter
 	url = https://github.com/rainlanguage/rain.interpreter
 	branch = 3.x
+[submodule "lib/rain.orderbook.interface"]
+	path = lib/rain.orderbook.interface
+	url = https://github.com/rainlanguage/rain.orderbook.interface
diff --git a/lib/rain.orderbook.interface b/lib/rain.orderbook.interface
new file mode 160000
index 000000000..8b6a0c27c
--- /dev/null
+++ b/lib/rain.orderbook.interface
@@ -0,0 +1 @@
+Subproject commit 8b6a0c27caa02b888177d000fb7605fb28834df5