diff --git a/docs/howto_custom_nginx.md b/docs/howto_custom_nginx.md
new file mode 100644
index 0000000000..2e8b76b817
--- /dev/null
+++ b/docs/howto_custom_nginx.md
@@ -0,0 +1,73 @@
+---
+title: Add Custom NGINX Configuration
+sidebar_label: Add Custom NGINX Configuration
+---
+
+Custom NGINX directives may be needed to support deployment-specific requirements or integrations without modifying the SSR-managed `nginx.conf` file. For example, custom directives can be used to integrate external authentication services such as CAC/PIV, add request handling behavior, or apply other supported NGINX settings.
+
+Use `/etc/nginx/default.d/` to add persistent custom NGINX directives to an SSR Conductor.
+
+Do not modify `/etc/nginx/nginx.conf` directly. SSR manages this file and may regenerate it during system startup or other operations.
+
+## Add the Configuration
+
+1. Create a `.conf` file in `/etc/nginx/default.d/` containing only the required NGINX directives. Do not add a `server` block. For example:
+
+```
+	sudo tee /etc/nginx/default.d/zz-custom.conf >/dev/null <<'EOF'
+	# Custom NGINX directives
+	auth_request /oauth2/auth;
+	error_page 401 = /oauth2/sign_in;
+	auth_request_set $auth_user $upstream_http_x_auth_request_user;
+	EOF
+```
+2. To preserve your custom NGINX file across image-based upgrades, create a data-transfer configuration file in `/etc/ssr-upgrade/data-transfer.d/`. For example:
+
+```
+	sudo tee /etc/ssr-upgrade/data-transfer.d/90-custom-nginx.yml >/dev/null <<'EOF'
+	version: "2.1"
+	data:
+	  - dataset: Custom NGINX configuration
+	    operations:
+	      - upgrade
+	      - reinstall
+	    files:
+	      - /etc/nginx/default.d/zz-custom.conf
+	EOF
+```
+3. Validate the configuration:
+
+	```
+	sudo nginx -t
+	```
+
+4. If validation succeeds, reload NGINX:
+
+	```
+	sudo systemctl reload nginx
+	```
+
+5. Confirm that the custom file is included:
+
+	```
+	sudo nginx -T 2>&1 | grep -n "zz-custom.conf"
+	```
+
+## Remove the Configuration
+
+1. Remove the custom file:
+
+	```
+	sudo rm -f /etc/nginx/default.d/zz-custom.conf
+	```
+
+2. Validate and reload NGINX:
+
+	```
+	sudo nginx -t
+	sudo systemctl reload nginx
+	```
+
+:::note
+If `nginx -t` reports an error, review the custom directives for invalid syntax, unsupported directives, or an incorrect configuration context.
+:::
diff --git a/sidebars.js b/sidebars.js
index a5b63f73db..1eff00626f 100644
--- a/sidebars.js
+++ b/sidebars.js
@@ -342,6 +342,7 @@ module.exports = {
           "config_in-memory_metrics",
           "howto_ms365",
           "howto_extend_gui_nav",
+          "howto_custom_nginx",
           ],
         },
         {