diff --git a/roles/xnat/tasks/settings_files.yml b/roles/xnat/tasks/settings_files.yml
index d538ced3..b832ec16 100644
--- a/roles/xnat/tasks/settings_files.yml
+++ b/roles/xnat/tasks/settings_files.yml
@@ -9,6 +9,15 @@
     force: true
   notify: Restart tomcat
 
+- name: "Validate xnat_config.site_name: {{ xnat_config.site_name }}"
+  ansible.builtin.assert:
+    that:
+      - xnat_config.site_name is match('^[A-Za-z][A-Za-z0-9_]*$')
+    fail_msg: >
+      xnat_config.site_name must start with a letter and contain only
+      letters, numbers, and underscores
+    success_msg: xnat_config.site_name is valid
+
 - name: "Configure prefs-init"
   ansible.builtin.template:
     src: "prefs-init.j2"