diff --git a/CHANGELOG.md b/CHANGELOG.md
index b97a201dfdc1..99ae3f8f5a1a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -16,6 +16,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Add missing utilities that exist in v3, such as `resize`, `fill-none`, `accent-none`, `drop-shadow-none`, and negative `hue-rotate` and `backdrop-hue-rotate` utilities ([#13971](https://github.com/tailwindlabs/tailwindcss/pull/13971))
 - Don’t allow at-rule-only variants to be compounded ([#14015](https://github.com/tailwindlabs/tailwindcss/pull/14015))
 - Ensure compound variants work with variants with multiple selectors ([#14016](https://github.com/tailwindlabs/tailwindcss/pull/14016))
+- Attribute selectors in `data-*` and `aria-*` modifiers are now wrapped in quotation marks by default, allowing numbers and spaces in them ([#14040])(https://github.com/tailwindlabs/tailwindcss/pull/14037)
 
 ### Added
 
diff --git a/packages/tailwindcss/src/variants.test.ts b/packages/tailwindcss/src/variants.test.ts
index 5fb6b4f2273e..d27da76387c3 100644
--- a/packages/tailwindcss/src/variants.test.ts
+++ b/packages/tailwindcss/src/variants.test.ts
@@ -1756,16 +1756,21 @@ test('aria', () => {
     run([
       'aria-checked:flex',
       'aria-[invalid=spelling]:flex',
+      'aria-[valuenow=1]:flex',
 
       'group-aria-[modal]:flex',
       'group-aria-checked:flex',
+      'group-aria-[valuenow=1]:flex',
       'group-aria-[modal]/parent-name:flex',
       'group-aria-checked/parent-name:flex',
+      'group-aria-[valuenow=1]/parent-name:flex',
 
       'peer-aria-[modal]:flex',
       'peer-aria-checked:flex',
+      'peer-aria-[valuenow=1]:flex',
       'peer-aria-[modal]/parent-name:flex',
       'peer-aria-checked/parent-name:flex',
+      'peer-aria-[valuenow=1]/parent-name:flex',
     ]),
   ).toMatchInlineSnapshot(`
     ".group-aria-\\[modal\\]\\:flex:is(:where(.group)[aria-modal] *) {
@@ -1776,6 +1781,10 @@ test('aria', () => {
       display: flex;
     }
 
+    .group-aria-\\[valuenow\\=1\\]\\:flex:is(:where(.group)[aria-valuenow="1"] *) {
+      display: flex;
+    }
+
     .group-aria-\\[modal\\]\\/parent-name\\:flex:is(:where(.group\\/parent-name)[aria-modal] *) {
       display: flex;
     }
@@ -1784,6 +1793,10 @@ test('aria', () => {
       display: flex;
     }
 
+    .group-aria-\\[valuenow\\=1\\]\\/parent-name\\:flex:is(:where(.group\\/parent-name)[aria-valuenow="1"] *) {
+      display: flex;
+    }
+
     .peer-aria-\\[modal\\]\\:flex:is(:where(.peer)[aria-modal] ~ *) {
       display: flex;
     }
@@ -1792,6 +1805,10 @@ test('aria', () => {
       display: flex;
     }
 
+    .peer-aria-\\[valuenow\\=1\\]\\:flex:is(:where(.peer)[aria-valuenow="1"] ~ *) {
+      display: flex;
+    }
+
     .peer-aria-\\[modal\\]\\/parent-name\\:flex:is(:where(.peer\\/parent-name)[aria-modal] ~ *) {
       display: flex;
     }
@@ -1800,12 +1817,20 @@ test('aria', () => {
       display: flex;
     }
 
+    .peer-aria-\\[valuenow\\=1\\]\\/parent-name\\:flex:is(:where(.peer\\/parent-name)[aria-valuenow="1"] ~ *) {
+      display: flex;
+    }
+
     .aria-checked\\:flex[aria-checked="true"] {
       display: flex;
     }
 
     .aria-\\[invalid\\=spelling\\]\\:flex[aria-invalid="spelling"] {
       display: flex;
+    }
+
+    .aria-\\[valuenow\\=1\\]\\:flex[aria-valuenow="1"] {
+      display: flex;
     }"
   `)
   expect(run(['aria-checked/foo:flex', 'aria-[invalid=spelling]/foo:flex'])).toEqual('')
@@ -1816,12 +1841,26 @@ test('data', () => {
     run([
       'data-disabled:flex',
       'data-[potato=salad]:flex',
+      'data-[foo=1]:flex',
+      'data-[foo=bar_baz]:flex',
+      "data-[foo$='bar'_i]:flex",
+      'data-[foo$=bar_baz_i]:flex',
 
       'group-data-[disabled]:flex',
       'group-data-[disabled]/parent-name:flex',
+      'group-data-[foo=1]:flex',
+      'group-data-[foo=1]/parent-name:flex',
+      'group-data-[foo=bar baz]/parent-name:flex',
+      "group-data-[foo$='bar'_i]/parent-name:flex",
+      'group-data-[foo$=bar_baz_i]/parent-name:flex',
 
       'peer-data-[disabled]:flex',
       'peer-data-[disabled]/parent-name:flex',
+      'peer-data-[foo=1]:flex',
+      'peer-data-[foo=1]/parent-name:flex',
+      'peer-data-[foo=bar baz]/parent-name:flex',
+      "peer-data-[foo$='bar'_i]/parent-name:flex",
+      'peer-data-[foo$=bar_baz_i]/parent-name:flex',
     ]),
   ).toMatchInlineSnapshot(`
     ".group-data-\\[disabled\\]\\:flex:is(:where(.group)[data-disabled] *) {
@@ -1832,6 +1871,26 @@ test('data', () => {
       display: flex;
     }
 
+    .group-data-\\[foo\\=1\\]\\:flex:is(:where(.group)[data-foo="1"] *) {
+      display: flex;
+    }
+
+    .group-data-\\[foo\\=1\\]\\/parent-name\\:flex:is(:where(.group\\/parent-name)[data-foo="1"] *) {
+      display: flex;
+    }
+
+    .group-data-\\[foo\\=bar\\ baz\\]\\/parent-name\\:flex:is(:where(.group\\/parent-name)[data-foo="bar baz"] *) {
+      display: flex;
+    }
+
+    .group-data-\\[foo\\$\\=\\'bar\\'_i\\]\\/parent-name\\:flex:is(:where(.group\\/parent-name)[data-foo$="bar" i] *) {
+      display: flex;
+    }
+
+    .group-data-\\[foo\\$\\=bar_baz_i\\]\\/parent-name\\:flex:is(:where(.group\\/parent-name)[data-foo$="bar baz" i] *) {
+      display: flex;
+    }
+
     .peer-data-\\[disabled\\]\\:flex:is(:where(.peer)[data-disabled] ~ *) {
       display: flex;
     }
@@ -1840,12 +1899,48 @@ test('data', () => {
       display: flex;
     }
 
+    .peer-data-\\[foo\\=1\\]\\:flex:is(:where(.peer)[data-foo="1"] ~ *) {
+      display: flex;
+    }
+
+    .peer-data-\\[foo\\=1\\]\\/parent-name\\:flex:is(:where(.peer\\/parent-name)[data-foo="1"] ~ *) {
+      display: flex;
+    }
+
+    .peer-data-\\[foo\\=bar\\ baz\\]\\/parent-name\\:flex:is(:where(.peer\\/parent-name)[data-foo="bar baz"] ~ *) {
+      display: flex;
+    }
+
+    .peer-data-\\[foo\\$\\=\\'bar\\'_i\\]\\/parent-name\\:flex:is(:where(.peer\\/parent-name)[data-foo$="bar" i] ~ *) {
+      display: flex;
+    }
+
+    .peer-data-\\[foo\\$\\=bar_baz_i\\]\\/parent-name\\:flex:is(:where(.peer\\/parent-name)[data-foo$="bar baz" i] ~ *) {
+      display: flex;
+    }
+
     .data-disabled\\:flex[data-disabled] {
       display: flex;
     }
 
     .data-\\[potato\\=salad\\]\\:flex[data-potato="salad"] {
       display: flex;
+    }
+
+    .data-\\[foo\\=1\\]\\:flex[data-foo="1"] {
+      display: flex;
+    }
+
+    .data-\\[foo\\=bar_baz\\]\\:flex[data-foo="bar baz"] {
+      display: flex;
+    }
+
+    .data-\\[foo\\$\\=\\'bar\\'_i\\]\\:flex[data-foo$="bar" i] {
+      display: flex;
+    }
+
+    .data-\\[foo\\$\\=bar_baz_i\\]\\:flex[data-foo$="bar baz" i] {
+      display: flex;
     }"
   `)
   expect(run(['data-disabled/foo:flex', 'data-[potato=salad]/foo:flex'])).toEqual('')
diff --git a/packages/tailwindcss/src/variants.ts b/packages/tailwindcss/src/variants.ts
index 909cfef22b6a..8a08bb787035 100644
--- a/packages/tailwindcss/src/variants.ts
+++ b/packages/tailwindcss/src/variants.ts
@@ -513,7 +513,7 @@ export function createVariants(theme: Theme): Variants {
     if (!variant.value || variant.modifier) return null
 
     if (variant.value.kind === 'arbitrary') {
-      ruleNode.nodes = [rule(`&[aria-${variant.value.value}]`, ruleNode.nodes)]
+      ruleNode.nodes = [rule(`&[aria-${quoteAttributeValue(variant.value.value)}]`, ruleNode.nodes)]
     } else {
       ruleNode.nodes = [rule(`&[aria-${variant.value.value}="true"]`, ruleNode.nodes)]
     }
@@ -534,7 +534,7 @@ export function createVariants(theme: Theme): Variants {
   variants.functional('data', (ruleNode, variant) => {
     if (!variant.value || variant.modifier) return null
 
-    ruleNode.nodes = [rule(`&[data-${variant.value.value}]`, ruleNode.nodes)]
+    ruleNode.nodes = [rule(`&[data-${quoteAttributeValue(variant.value.value)}]`, ruleNode.nodes)]
   })
 
   variants.functional('nth', (ruleNode, variant) => {
@@ -904,3 +904,31 @@ export function createVariants(theme: Theme): Variants {
 
   return variants
 }
+
+function quoteAttributeValue(value: string) {
+  if (value.includes('=')) {
+    value = value.replace(/(=.*)/g, (_fullMatch, match) => {
+      // If the value is already quoted, skip.
+      if (match[1] === "'" || match[1] === '"') {
+        return match
+      }
+
+      // Handle regex flags on unescaped values
+      if (match.length > 2) {
+        let trailingCharacter = match[match.length - 1]
+        if (
+          match[match.length - 2] === ' ' &&
+          (trailingCharacter === 'i' ||
+            trailingCharacter === 'I' ||
+            trailingCharacter === 's' ||
+            trailingCharacter === 'S')
+        ) {
+          return `="${match.slice(1, -2)}" ${match[match.length - 1]}`
+        }
+      }
+
+      return `="${match.slice(1)}"`
+    })
+  }
+  return value
+}