diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000..e440eee
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,3 @@
+[submodule "hiop"]
+	path = hiop
+	url = https://github.com/LLNL/hiop
diff --git a/hiop b/hiop
new file mode 160000
index 0000000..2252b90
--- /dev/null
+++ b/hiop
@@ -0,0 +1 @@
+Subproject commit 2252b90bc40f86b8d842da6fec30105feddbf647