diff --git a/client/scss/components/_icons.scss b/client/scss/components/_icons.scss
index 1a1e9a18ef..6ea1298e44 100644
--- a/client/scss/components/_icons.scss
+++ b/client/scss/components/_icons.scss
@@ -35,6 +35,8 @@
 // Icon factory methods
 // =============================================================================
 
+// RemovedInWagtail60Warning
+// Font icons unused in Wagtail core, kept for backwards compatibility with third-party customisations.
 @each $icon, $content in $icons {
   .icon-#{$icon}:before {
     content: string.quote(#{$content});
diff --git a/client/scss/settings/_variables.icons.scss b/client/scss/settings/_variables.icons.scss
index 6666adfca8..e2e998c34f 100644
--- a/client/scss/settings/_variables.icons.scss
+++ b/client/scss/settings/_variables.icons.scss
@@ -1,4 +1,7 @@
 @use 'sass:map';
+
+// RemovedInWagtail60Warning
+// Font icons unused in Wagtail core, kept for backwards compatibility with third-party customisations.
 $icons: (
   'arrow-down-big': '\e030',
   'arrow-down': '\e01a',