diff --git a/.changeset/fix-fab-extended-width.md b/.changeset/fix-fab-extended-width.md
new file mode 100644
index 0000000000..431f2064ee
--- /dev/null
+++ b/.changeset/fix-fab-extended-width.md
@@ -0,0 +1,5 @@
+---
+'@graphcommerce/next-ui': patch
+---
+
+Fix: `<Fab variant="extended">` no longer gets a fixed `width` from `MuiFabSizes`. The size-based width/height variants are now scoped to `variant: 'circular'` only, so extended Fabs can grow with their label (controlled via `min-width` instead) as MUI intends. Previously every extended Fab without an explicit `size` matched the default `large` rule and was forced to 54px wide.
diff --git a/packages/next-ui/Theme/MuiFab.ts b/packages/next-ui/Theme/MuiFab.ts
index c81b9945d2..7cb2882d37 100644
--- a/packages/next-ui/Theme/MuiFab.ts
+++ b/packages/next-ui/Theme/MuiFab.ts
@@ -80,11 +80,14 @@ const sizes: FabSize[] = [
 /**
  * This defines the sizes for the added responsive variant.
  *
+ * Only applied to circular (default) Fabs — extended Fabs must keep `width: auto` and rely on their
+ * content + `min-width`, otherwise they collapse to a fixed square regardless of label.
+ *
  * To override the sizes, please do not add variant declarations direcly, but modify
  * `yourTheme.components.MuiFabExtra.sizes` instead.
  */
 export const MuiFabSizes: FabVariants = sizes.map((size) => ({
-  props: { size },
+  props: { size, variant: 'circular' },
   style: ({ theme }) => fabWidthHeight(size, theme),
 }))