diff --git a/robots.txt b/robots.txt
new file mode 100644
index 0000000000000..bb98e1ad94a9d
--- /dev/null
+++ b/robots.txt
@@ -0,0 +1,5 @@
+# Do not let search engines index the PyData theme preview site
+# during the live testing phase.
+# https://github.com/scikit-learn/scikit-learn/pull/28353
+User-agent: *
+Disallow: /_pst_preview/