diff --git a/.changeset/old-moles-sort.md b/.changeset/old-moles-sort.md
new file mode 100644
index 0000000000..2ad24946c2
--- /dev/null
+++ b/.changeset/old-moles-sort.md
@@ -0,0 +1,5 @@
+---
+"stylelint": patch
+---
+
+Fixed: `unit-no-unknown` false positives for font-relative length units
diff --git a/lib/reference/units.js b/lib/reference/units.js
index b7ee630b0a..72ab5ead0d 100644
--- a/lib/reference/units.js
+++ b/lib/reference/units.js
@@ -3,13 +3,19 @@
 const uniteSets = require('../utils/uniteSets.js');
 
 const lengthUnits = new Set([
-	// Relative length units
+	// Font-relative length units
+	'cap',
+	'ch',
 	'em',
 	'ex',
-	'ch',
+	'ic',
+	'lh',
+	'rcap',
+	'rch',
 	'rem',
+	'rex',
+	'ric',
 	'rlh',
-	'lh',
 	// Viewport-percentage lengths
 	'dvh',
 	'dvmax',
diff --git a/lib/rules/unit-no-unknown/__tests__/index.js b/lib/rules/unit-no-unknown/__tests__/index.js
index 2dc5fc82a6..5ebd859f57 100644
--- a/lib/rules/unit-no-unknown/__tests__/index.js
+++ b/lib/rules/unit-no-unknown/__tests__/index.js
@@ -239,6 +239,9 @@ testRule({
 			code: 'a { image-resolution: 1x; }',
 			description: 'ignore `x` unit in image-resolution',
 		},
+		{
+			code: 'a { width: 8ic; }',
+		},
 	],
 
 	reject: [