diff --git a/.gitignore b/.gitignore
index 4f86b320..ca3a87cb 100644
--- a/.gitignore
+++ b/.gitignore
@@ -143,3 +143,6 @@ src/stcal/_version.py
 
 # auto-generated API docs
 docs/source/api
+
+# C files auto-generated by cython
+**/*.c