diff --git a/packages/compiler-core/__tests__/transforms/__snapshots__/vIf.spec.ts.snap b/packages/compiler-core/__tests__/transforms/__snapshots__/vIf.spec.ts.snap
index 65ee73c46f4..648d61cec12 100644
--- a/packages/compiler-core/__tests__/transforms/__snapshots__/vIf.spec.ts.snap
+++ b/packages/compiler-core/__tests__/transforms/__snapshots__/vIf.spec.ts.snap
@@ -86,6 +86,129 @@ return function render(_ctx, _cache) {
 }"
 `;
 
+exports[`compiler: v-if > codegen > user-defined keys > avoid duplicate keys 1`] = `
+"const _Vue = Vue
+
+return function render(_ctx, _cache) {
+  with (_ctx) {
+    const { mergeProps: _mergeProps, openBlock: _openBlock, createElementBlock: _createElementBlock, createCommentVNode: _createCommentVNode } = _Vue
+
+    return ok
+      ? (_openBlock(), _createElementBlock("div", _mergeProps({ key: "custom_key" }, obj), null, 16 /* FULL_PROPS */))
+      : _createCommentVNode("v-if", true)
+  }
+}"
+`;
+
+exports[`compiler: v-if > codegen > user-defined keys > correct key matching 1`] = `
+"const _Vue = Vue
+const { createCommentVNode: _createCommentVNode } = _Vue
+
+const _hoisted_1 = Symbol()
+
+return function render(_ctx, _cache) {
+  with (_ctx) {
+    const { normalizeProps: _normalizeProps, guardReactiveProps: _guardReactiveProps, openBlock: _openBlock, createElementBlock: _createElementBlock, mergeProps: _mergeProps, createCommentVNode: _createCommentVNode, Fragment: _Fragment } = _Vue
+
+    return (_openBlock(), _createElementBlock(_Fragment, null, [
+      ok
+        ? (_openBlock(), _createElementBlock("div", _normalizeProps(_mergeProps({ key: 0 }, separate)), null, 16 /* FULL_PROPS */))
+        : _createCommentVNode("v-if", true),
+      (_openBlock(), _createElementBlock("div", _mergeProps({ key: 123 }, other1), null, 16 /* FULL_PROPS */)),
+      ok1
+        ? (_openBlock(), _createElementBlock("div", _normalizeProps(_mergeProps({ key: _hoisted_1 }, obj1)), null, 16 /* FULL_PROPS */))
+        : (_openBlock(), _createElementBlock("div", _mergeProps({ key: 0 }, obj2), null, 16 /* FULL_PROPS */))
+    ], 64 /* STABLE_FRAGMENT */))
+  }
+}"
+`;
+
+exports[`compiler: v-if > codegen > user-defined keys > key on v-else 1`] = `
+"const _Vue = Vue
+const { createCommentVNode: _createCommentVNode } = _Vue
+
+const _hoisted_1 = Symbol()
+const _hoisted_2 = Symbol()
+
+return function render(_ctx, _cache) {
+  with (_ctx) {
+    const { normalizeProps: _normalizeProps, guardReactiveProps: _guardReactiveProps, openBlock: _openBlock, createElementBlock: _createElementBlock, mergeProps: _mergeProps, createCommentVNode: _createCommentVNode } = _Vue
+
+    return ok1
+      ? (_openBlock(), _createElementBlock("div", _normalizeProps(_mergeProps({ key: _hoisted_1 }, obj1)), null, 16 /* FULL_PROPS */))
+      : ok2
+        ? (_openBlock(), _createElementBlock("div", _normalizeProps(_mergeProps({ key: _hoisted_2 }, obj2)), null, 16 /* FULL_PROPS */))
+        : (_openBlock(), _createElementBlock("div", _mergeProps({ key: 0 }, obj3), null, 16 /* FULL_PROPS */))
+  }
+}"
+`;
+
+exports[`compiler: v-if > codegen > user-defined keys > key on v-else with misc irrelevant nodes between 1`] = `
+"const _Vue = Vue
+const { createElementVNode: _createElementVNode, createCommentVNode: _createCommentVNode } = _Vue
+
+const _hoisted_1 = Symbol()
+const _hoisted_2 = Symbol()
+
+return function render(_ctx, _cache) {
+  with (_ctx) {
+    const { normalizeProps: _normalizeProps, guardReactiveProps: _guardReactiveProps, openBlock: _openBlock, createElementBlock: _createElementBlock, mergeProps: _mergeProps, createCommentVNode: _createCommentVNode, createElementVNode: _createElementVNode, Fragment: _Fragment } = _Vue
+
+    return ok1
+      ? (_openBlock(), _createElementBlock("div", _normalizeProps(_mergeProps({ key: _hoisted_1 }, obj1)), null, 16 /* FULL_PROPS */))
+      : ok2
+        ? (_openBlock(), _createElementBlock(_Fragment, { key: _hoisted_2 }, [
+            _createCommentVNode("comment1"),
+            _createElementVNode("div", _normalizeProps(_guardReactiveProps(obj2)), null, 16 /* FULL_PROPS */)
+          ], 2112 /* STABLE_FRAGMENT, DEV_ROOT_FRAGMENT */))
+        : (_openBlock(), _createElementBlock(_Fragment, { key: 0 }, [
+            _createCommentVNode("comment2"),
+            (_openBlock(), _createElementBlock("div", _mergeProps({ key: 0 }, obj3), null, 16 /* FULL_PROPS */))
+          ], 2112 /* STABLE_FRAGMENT, DEV_ROOT_FRAGMENT */))
+  }
+}"
+`;
+
+exports[`compiler: v-if > codegen > user-defined keys > key on v-else-if 1`] = `
+"const _Vue = Vue
+const { createCommentVNode: _createCommentVNode } = _Vue
+
+const _hoisted_1 = Symbol()
+const _hoisted_2 = Symbol()
+
+return function render(_ctx, _cache) {
+  with (_ctx) {
+    const { normalizeProps: _normalizeProps, guardReactiveProps: _guardReactiveProps, openBlock: _openBlock, createElementBlock: _createElementBlock, mergeProps: _mergeProps, createCommentVNode: _createCommentVNode } = _Vue
+
+    return ok1
+      ? (_openBlock(), _createElementBlock("div", _normalizeProps(_mergeProps({ key: _hoisted_1 }, obj1)), null, 16 /* FULL_PROPS */))
+      : ok2
+        ? (_openBlock(), _createElementBlock("div", _mergeProps({ key: 0 }, obj2), null, 16 /* FULL_PROPS */))
+        : (_openBlock(), _createElementBlock("div", _normalizeProps(_mergeProps({ key: _hoisted_2 }, obj3)), null, 16 /* FULL_PROPS */))
+  }
+}"
+`;
+
+exports[`compiler: v-if > codegen > user-defined keys > key on v-if 1`] = `
+"const _Vue = Vue
+const { createCommentVNode: _createCommentVNode } = _Vue
+
+const _hoisted_1 = Symbol()
+const _hoisted_2 = Symbol()
+
+return function render(_ctx, _cache) {
+  with (_ctx) {
+    const { mergeProps: _mergeProps, openBlock: _openBlock, createElementBlock: _createElementBlock, createCommentVNode: _createCommentVNode, normalizeProps: _normalizeProps, guardReactiveProps: _guardReactiveProps } = _Vue
+
+    return ok1
+      ? (_openBlock(), _createElementBlock("div", _mergeProps({ key: 1 }, obj1), null, 16 /* FULL_PROPS */))
+      : ok2
+        ? (_openBlock(), _createElementBlock("div", _normalizeProps(_mergeProps({ key: _hoisted_1 }, obj2)), null, 16 /* FULL_PROPS */))
+        : (_openBlock(), _createElementBlock("div", _normalizeProps(_mergeProps({ key: _hoisted_2 }, obj3)), null, 16 /* FULL_PROPS */))
+  }
+}"
+`;
+
 exports[`compiler: v-if > codegen > v-if + v-else 1`] = `
 "const _Vue = Vue
 
diff --git a/packages/compiler-core/__tests__/transforms/vIf.spec.ts b/packages/compiler-core/__tests__/transforms/vIf.spec.ts
index 1e0067aa32a..2e030ae040a 100644
--- a/packages/compiler-core/__tests__/transforms/vIf.spec.ts
+++ b/packages/compiler-core/__tests__/transforms/vIf.spec.ts
@@ -21,6 +21,7 @@ import {
   type CompilerOptions,
   TO_HANDLERS,
   generate,
+  transformBind,
   transformVBindShorthand,
 } from '../../src'
 import {
@@ -37,6 +38,7 @@ function parseWithIfTransform(
   options: CompilerOptions = {},
   returnIndex: number = 0,
   childrenLen: number = 1,
+  expectAllChildrenIfNodes: boolean = true,
 ) {
   const ast = parse(template, options)
   transform(ast, {
@@ -50,8 +52,10 @@ function parseWithIfTransform(
   })
   if (!options.onError) {
     expect(ast.children.length).toBe(childrenLen)
-    for (let i = 0; i < childrenLen; i++) {
-      expect(ast.children[i].type).toBe(NodeTypes.IF)
+    if (expectAllChildrenIfNodes) {
+      for (let i = 0; i < childrenLen; i++) {
+        expect(ast.children[i].type).toBe(NodeTypes.IF)
+      }
     }
   }
   return {
@@ -670,21 +674,120 @@ describe('compiler: v-if', () => {
       expect(branch1.props).toMatchObject(createObjectMatcher({ key: `[0]` }))
     })
 
-    // #6631
-    test('avoid duplicate keys', () => {
-      const {
-        node: { codegenNode },
-      } = parseWithIfTransform(`<div v-if="ok" key="custom_key" v-bind="obj"/>`)
-      const branch1 = codegenNode.consequent as VNodeCall
-      expect(branch1.props).toMatchObject({
-        type: NodeTypes.JS_CALL_EXPRESSION,
-        callee: MERGE_PROPS,
-        arguments: [
-          createObjectMatcher({
-            key: 'custom_key',
-          }),
-          { content: `obj` },
-        ],
+    describe('user-defined keys', () => {
+      // #6631
+      test('avoid duplicate keys', () => {
+        const {
+          root,
+          node: { codegenNode },
+        } = parseWithIfTransform(
+          `<div v-if="ok" key="custom_key" v-bind="obj"/>`,
+        )
+        const branch1 = codegenNode.consequent as VNodeCall
+        expect(branch1.props).toMatchObject({
+          type: NodeTypes.JS_CALL_EXPRESSION,
+          callee: MERGE_PROPS,
+          arguments: [
+            createObjectMatcher({
+              key: 'custom_key',
+            }),
+            { content: `obj` },
+          ],
+        })
+        expect(generate(root).code).toMatchSnapshot()
+      })
+
+      test('key on v-if', () => {
+        const { root } = parseWithIfTransform(
+          `<div v-if="ok1" :key="1" v-bind="obj1"/><div v-else-if="ok2" v-bind="obj2"/><div v-else v-bind="obj3"/>`,
+          { directiveTransforms: { bind: transformBind } },
+        )
+        expect(root.hoists).toMatchObject([
+          { content: 'Symbol()' },
+          { content: 'Symbol()' },
+        ])
+
+        const code = generate(root).code
+        expect(code).toContain('_mergeProps({ key: 1 }, obj1)')
+        expect(code).toContain('_mergeProps({ key: _hoisted_1 }, obj2)')
+        expect(code).toContain('_mergeProps({ key: _hoisted_2 }, obj3)')
+        expect(code).toMatchSnapshot()
+      })
+
+      test('key on v-else-if', () => {
+        const { root } = parseWithIfTransform(
+          `<div v-if="ok1" v-bind="obj1"/><div v-else-if="ok2" :key="0" v-bind="obj2"/><div v-else v-bind="obj3"/>`,
+          { directiveTransforms: { bind: transformBind } },
+        )
+        expect(root.hoists).toMatchObject([
+          { content: 'Symbol()' },
+          { content: 'Symbol()' },
+        ])
+
+        const code = generate(root).code
+        expect(code).toContain('_mergeProps({ key: _hoisted_1 }, obj1)')
+        expect(code).toContain('_mergeProps({ key: 0 }, obj2)')
+        expect(code).toContain('_mergeProps({ key: _hoisted_2 }, obj3)')
+        expect(code).toMatchSnapshot()
+      })
+
+      test('key on v-else', () => {
+        const { root } = parseWithIfTransform(
+          `<div v-if="ok1" v-bind="obj1"/><div v-else-if="ok2" v-bind="obj2"/><div v-else :key="0" v-bind="obj3"/>`,
+          { directiveTransforms: { bind: transformBind } },
+        )
+        expect(root.hoists).toMatchObject([
+          { content: 'Symbol()' },
+          { content: 'Symbol()' },
+        ])
+
+        const code = generate(root).code
+        expect(code).toContain('_mergeProps({ key: _hoisted_1 }, obj1)')
+        expect(code).toContain('_mergeProps({ key: _hoisted_2 }, obj2)')
+        expect(code).toContain('_mergeProps({ key: 0 }, obj3)')
+        expect(code).toMatchSnapshot()
+      })
+
+      test('key on v-else with misc irrelevant nodes between', () => {
+        const { root } = parseWithIfTransform(
+          `<div v-if="ok1" v-bind="obj1"/> <!--comment1--> <div v-else-if="ok2" v-bind="obj2"/> <!--comment2--> <div v-else :key="0" v-bind="obj3"/>`,
+          { directiveTransforms: { bind: transformBind } },
+          0,
+          1,
+          false,
+        )
+        expect(root.hoists).toMatchObject([
+          { content: 'Symbol()' },
+          { content: 'Symbol()' },
+        ])
+
+        const code = generate(root).code
+        expect(code).toContain('_mergeProps({ key: _hoisted_1 }, obj1)')
+        expect(code).toContain(
+          '_createElementBlock(_Fragment, { key: _hoisted_2 }',
+        )
+        expect(code).toContain('_normalizeProps(_guardReactiveProps(obj2))')
+        expect(code).toContain('_mergeProps({ key: 0 }, obj3)')
+        expect(code).toMatchSnapshot()
+      })
+
+      test('correct key matching', () => {
+        const { root } = parseWithIfTransform(
+          `<div v-if="ok" v-bind="separate"/><div :key="123" v-bind="other1" /><div v-if="ok1" v-bind="obj1"/><div v-else :key="0" v-bind="obj2"/>`,
+          { directiveTransforms: { bind: transformBind } },
+          0,
+          3,
+          false,
+        )
+        expect(root.hoists).toMatchObject([{ content: 'Symbol()' }])
+
+        const code = generate(root).code
+        // not part of if-block with a key anywhere so expect
+        expect(code).toContain('_mergeProps({ key: 0 }, separate)')
+        expect(code).toContain('_mergeProps({ key: 123 }, other1)')
+        expect(code).toContain('_mergeProps({ key: _hoisted_1 }, obj1)')
+        expect(code).toContain('_mergeProps({ key: 0 }, obj2)')
+        expect(code).toMatchSnapshot()
       })
     })
 
diff --git a/packages/compiler-core/src/ast.ts b/packages/compiler-core/src/ast.ts
index 2d6df9d9010..5a436138822 100644
--- a/packages/compiler-core/src/ast.ts
+++ b/packages/compiler-core/src/ast.ts
@@ -280,6 +280,7 @@ export interface IfNode extends Node {
   type: NodeTypes.IF
   branches: IfBranchNode[]
   codegenNode?: IfConditionalExpression | CacheExpression // <div v-if v-once>
+  anyBranchesHaveUserDefinedKey?: boolean
 }
 
 export interface IfBranchNode extends Node {
diff --git a/packages/compiler-core/src/transforms/vIf.ts b/packages/compiler-core/src/transforms/vIf.ts
index 74575322d46..f120ef3da0b 100644
--- a/packages/compiler-core/src/transforms/vIf.ts
+++ b/packages/compiler-core/src/transforms/vIf.ts
@@ -18,6 +18,7 @@ import {
   type MemoExpression,
   NodeTypes,
   type SimpleExpressionNode,
+  type TemplateChildNode,
   convertToBlock,
   createCallExpression,
   createConditionalExpression,
@@ -59,6 +60,7 @@ export const transformIf: NodeTransform = createStructuralDirectiveTransform(
           ifNode.codegenNode = createCodegenNodeForBranch(
             branch,
             key,
+            !!ifNode.anyBranchesHaveUserDefinedKey,
             context,
           ) as IfConditionalExpression
         } else {
@@ -67,6 +69,7 @@ export const transformIf: NodeTransform = createStructuralDirectiveTransform(
           parentCondition.alternate = createCodegenNodeForBranch(
             branch,
             key + ifNode.branches.length - 1,
+            !!ifNode.anyBranchesHaveUserDefinedKey,
             context,
           )
         }
@@ -109,10 +112,37 @@ export function processIf(
 
   if (dir.name === 'if') {
     const branch = createIfBranch(node, dir)
+    const siblings = context.parent!.children
+    let anyBranchesHaveUserDefinedKey = !!branch.userKey
+    for (
+      let i = siblings.indexOf(node) + 1;
+      !anyBranchesHaveUserDefinedKey && i < siblings.length;
+      i++
+    ) {
+      const sibling = siblings[i]
+      if (
+        !sibling ||
+        sibling.type === NodeTypes.COMMENT ||
+        isEmptyTextNode(sibling)
+      ) {
+        continue
+      }
+
+      if (
+        sibling.type !== NodeTypes.ELEMENT ||
+        !(findDir(sibling, 'else-if') || findDir(sibling, 'else', true))
+      ) {
+        break
+      }
+
+      anyBranchesHaveUserDefinedKey = !!findProp(sibling, 'key')
+    }
+
     const ifNode: IfNode = {
       type: NodeTypes.IF,
       loc: cloneLoc(node.loc),
       branches: [branch],
+      anyBranchesHaveUserDefinedKey,
     }
     context.replaceNode(ifNode)
     if (processCodegen) {
@@ -131,11 +161,7 @@ export function processIf(
         continue
       }
 
-      if (
-        sibling &&
-        sibling.type === NodeTypes.TEXT &&
-        !sibling.content.trim().length
-      ) {
+      if (sibling && isEmptyTextNode(sibling)) {
         context.removeNode(sibling)
         continue
       }
@@ -220,12 +246,18 @@ function createIfBranch(node: ElementNode, dir: DirectiveNode): IfBranchNode {
 function createCodegenNodeForBranch(
   branch: IfBranchNode,
   keyIndex: number,
+  hasAnyUserDefinedKeys: boolean,
   context: TransformContext,
 ): IfConditionalExpression | BlockCodegenNode | MemoExpression {
   if (branch.condition) {
     return createConditionalExpression(
       branch.condition,
-      createChildrenCodegenNode(branch, keyIndex, context),
+      createChildrenCodegenNode(
+        branch,
+        keyIndex,
+        hasAnyUserDefinedKeys,
+        context,
+      ),
       // make sure to pass in asBlock: true so that the comment node call
       // closes the current block.
       createCallExpression(context.helper(CREATE_COMMENT), [
@@ -234,25 +266,35 @@ function createCodegenNodeForBranch(
       ]),
     ) as IfConditionalExpression
   } else {
-    return createChildrenCodegenNode(branch, keyIndex, context)
+    return createChildrenCodegenNode(
+      branch,
+      keyIndex,
+      hasAnyUserDefinedKeys,
+      context,
+    )
   }
 }
 
 function createChildrenCodegenNode(
   branch: IfBranchNode,
   keyIndex: number,
+  hasAnyUserDefinedKeys: boolean,
   context: TransformContext,
 ): BlockCodegenNode | MemoExpression {
   const { helper } = context
-  const keyProperty = createObjectProperty(
-    `key`,
-    createSimpleExpression(
-      `${keyIndex}`,
-      false,
-      locStub,
-      ConstantTypes.CAN_CACHE,
-    ),
-  )
+  const keyExp = branch.userKey
+    ? branch.userKey.type === NodeTypes.ATTRIBUTE
+      ? createSimpleExpression(branch.userKey.value!.content, true)
+      : branch.userKey.exp!
+    : hasAnyUserDefinedKeys
+      ? context.hoist('Symbol()')
+      : createSimpleExpression(
+          `${keyIndex}`,
+          false,
+          locStub,
+          ConstantTypes.CAN_CACHE,
+        )
+  const keyProperty = createObjectProperty(`key`, keyExp)
   const { children } = branch
   const firstChild = children[0]
   const needFragmentWrapper =
@@ -348,3 +390,7 @@ function getParentCondition(
     }
   }
 }
+
+function isEmptyTextNode(node: TemplateChildNode): boolean {
+  return node.type === NodeTypes.TEXT && !node.content.trim().length
+}