diff --git a/packages/vuetify/.eslintrc.js b/packages/vuetify/.eslintrc.js
index 78f656db0c4..22f0ed79e82 100644
--- a/packages/vuetify/.eslintrc.js
+++ b/packages/vuetify/.eslintrc.js
@@ -12,6 +12,7 @@ module.exports = {
   rules: {
     'no-console': 'error',
     'no-debugger': 'error',
+    'no-labels': 'off',
 
     // 'vue/html-self-closing': 'off',
     // 'vue/html-closing-bracket-spacing': 'off',
diff --git a/packages/vuetify/src/components/VAutocomplete/VAutocomplete.tsx b/packages/vuetify/src/components/VAutocomplete/VAutocomplete.tsx
index ea4ad190782..df611a5aa11 100644
--- a/packages/vuetify/src/components/VAutocomplete/VAutocomplete.tsx
+++ b/packages/vuetify/src/components/VAutocomplete/VAutocomplete.tsx
@@ -28,6 +28,7 @@ import { makeTransitionProps } from '@/composables/transition'
 import { computed, mergeProps, nextTick, ref, shallowRef, watch } from 'vue'
 import {
   checkPrintable,
+  deepEqual,
   ensureValidVNode,
   genericComponent,
   IN_BROWSER,
@@ -346,7 +347,7 @@ export const VAutocomplete = genericComponent<new <
       if (!item || item.props.disabled) return
 
       if (props.multiple) {
-        const index = model.value.findIndex(selection => props.valueComparator(selection.value, item.value))
+        const index = model.value.findIndex(selection => (props.valueComparator || deepEqual)(selection.value, item.value))
         const add = set == null ? !~index : set
 
         if (~index) {
diff --git a/packages/vuetify/src/components/VCombobox/VCombobox.tsx b/packages/vuetify/src/components/VCombobox/VCombobox.tsx
index 54014e7bc42..a386a3ce399 100644
--- a/packages/vuetify/src/components/VCombobox/VCombobox.tsx
+++ b/packages/vuetify/src/components/VCombobox/VCombobox.tsx
@@ -29,6 +29,7 @@ import { makeTransitionProps } from '@/composables/transition'
 import { computed, mergeProps, nextTick, ref, shallowRef, watch } from 'vue'
 import {
   checkPrintable,
+  deepEqual,
   ensureValidVNode,
   genericComponent,
   IN_BROWSER,
@@ -381,7 +382,7 @@ export const VCombobox = genericComponent<new <
       if (!item || item.props.disabled) return
 
       if (props.multiple) {
-        const index = model.value.findIndex(selection => props.valueComparator(selection.value, item.value))
+        const index = model.value.findIndex(selection => (props.valueComparator || deepEqual)(selection.value, item.value))
         const add = set == null ? !~index : set
 
         if (~index) {
@@ -446,7 +447,7 @@ export const VCombobox = genericComponent<new <
     watch(menu, () => {
       if (!props.hideSelected && menu.value && model.value.length) {
         const index = displayItems.value.findIndex(
-          item => model.value.some(s => props.valueComparator(s.value, item.value))
+          item => model.value.some(s => (props.valueComparator || deepEqual)(s.value, item.value))
         )
         IN_BROWSER && window.requestAnimationFrame(() => {
           index >= 0 && vVirtualScrollRef.value?.scrollToIndex(index)
diff --git a/packages/vuetify/src/components/VList/VList.tsx b/packages/vuetify/src/components/VList/VList.tsx
index c5cc5d8b490..dcd6c704728 100644
--- a/packages/vuetify/src/components/VList/VList.tsx
+++ b/packages/vuetify/src/components/VList/VList.tsx
@@ -23,7 +23,16 @@ import { makeVariantProps } from '@/composables/variant'
 
 // Utilities
 import { computed, ref, shallowRef, toRef } from 'vue'
-import { EventProp, focusChild, genericComponent, getPropertyFromItem, omit, propsFactory, useRender } from '@/util'
+import {
+  EventProp,
+  focusChild,
+  genericComponent,
+  getPropertyFromItem,
+  isPrimitive,
+  omit,
+  propsFactory,
+  useRender,
+} from '@/util'
 
 // Types
 import type { PropType } from 'vue'
@@ -35,10 +44,6 @@ export interface InternalListItem<T = any> extends ListItem<T> {
   type?: 'item' | 'subheader' | 'divider'
 }
 
-function isPrimitive (value: unknown): value is string | number | boolean {
-  return typeof value === 'string' || typeof value === 'number' || typeof value === 'boolean'
-}
-
 function transformItem (props: ItemProps & { itemType?: string }, item: any): InternalListItem {
   const type = getPropertyFromItem(item, props.itemType, 'item')
   const title = isPrimitive(item) ? item : getPropertyFromItem(item, props.itemTitle)
diff --git a/packages/vuetify/src/components/VSelect/VSelect.tsx b/packages/vuetify/src/components/VSelect/VSelect.tsx
index 88392f8d60b..65832dcc3f9 100644
--- a/packages/vuetify/src/components/VSelect/VSelect.tsx
+++ b/packages/vuetify/src/components/VSelect/VSelect.tsx
@@ -27,6 +27,7 @@ import { makeTransitionProps } from '@/composables/transition'
 import { computed, mergeProps, nextTick, ref, shallowRef, watch } from 'vue'
 import {
   checkPrintable,
+  deepEqual,
   ensureValidVNode,
   genericComponent,
   IN_BROWSER,
@@ -177,7 +178,7 @@ export const VSelect = genericComponent<new <
 
     const displayItems = computed(() => {
       if (props.hideSelected) {
-        return items.value.filter(item => !model.value.some(s => props.valueComparator(s, item)))
+        return items.value.filter(item => !model.value.some(s => (props.valueComparator || deepEqual)(s, item)))
       }
       return items.value
     })
@@ -262,7 +263,7 @@ export const VSelect = genericComponent<new <
       if (item.props.disabled) return
 
       if (props.multiple) {
-        const index = model.value.findIndex(selection => props.valueComparator(selection.value, item.value))
+        const index = model.value.findIndex(selection => (props.valueComparator || deepEqual)(selection.value, item.value))
         const add = set == null ? !~index : set
 
         if (~index) {
@@ -314,7 +315,7 @@ export const VSelect = genericComponent<new <
     watch(menu, () => {
       if (!props.hideSelected && menu.value && model.value.length) {
         const index = displayItems.value.findIndex(
-          item => model.value.some(s => props.valueComparator(s.value, item.value))
+          item => model.value.some(s => (props.valueComparator || deepEqual)(s.value, item.value))
         )
         IN_BROWSER && window.requestAnimationFrame(() => {
           index >= 0 && vVirtualScrollRef.value?.scrollToIndex(index)
diff --git a/packages/vuetify/src/composables/list-items.ts b/packages/vuetify/src/composables/list-items.ts
index 41d688a5416..d4f11fe5757 100644
--- a/packages/vuetify/src/composables/list-items.ts
+++ b/packages/vuetify/src/composables/list-items.ts
@@ -1,11 +1,11 @@
 // Utilities
-import { computed } from 'vue'
-import { deepEqual, getPropertyFromItem, omit, propsFactory } from '@/util'
+import { computed, shallowRef, toRaw, watchEffect } from 'vue'
+import { deepEqual, getPropertyFromItem, isPrimitive, omit, propsFactory } from '@/util'
 
 // Types
 import type { PropType } from 'vue'
 import type { InternalItem } from '@/composables/filter'
-import type { SelectItemKey } from '@/util'
+import type { Primitive, SelectItemKey } from '@/util'
 
 export interface ListItem<T = any> extends InternalItem<T> {
   title: string
@@ -24,7 +24,7 @@ export interface ItemProps {
   itemChildren: SelectItemKey
   itemProps: SelectItemKey
   returnObject: boolean
-  valueComparator: typeof deepEqual
+  valueComparator: typeof deepEqual | undefined
 }
 
 // Composables
@@ -50,10 +50,7 @@ export const makeItemsProps = propsFactory({
     default: 'props',
   },
   returnObject: Boolean,
-  valueComparator: {
-    type: Function as PropType<typeof deepEqual>,
-    default: deepEqual,
-  },
+  valueComparator: Function as PropType<typeof deepEqual>,
 }, 'list-items')
 
 export function transformItem (props: Omit<ItemProps, 'items'>, item: any): ListItem {
@@ -84,10 +81,11 @@ export function transformItem (props: Omit<ItemProps, 'items'>, item: any): List
 }
 
 export function transformItems (props: Omit<ItemProps, 'items'>, items: ItemProps['items']) {
-  const array: ListItem[] = []
+  const _props = toRaw(props)
 
+  const array: ListItem[] = []
   for (const item of items) {
-    array.push(transformItem(props, item))
+    array.push(transformItem(_props, item))
   }
 
   return array
@@ -97,15 +95,44 @@ export function useItems (props: ItemProps) {
   const items = computed(() => transformItems(props, props.items))
   const hasNullItem = computed(() => items.value.some(item => item.value === null))
 
-  function transformIn (value: any[]): ListItem[] {
-    // Cache unrefed values outside the loop
+  const itemsMap = shallowRef<Map<Primitive, ListItem[]>>(new Map())
+  const keylessItems = shallowRef<ListItem[]>([])
+  watchEffect(() => {
     const _items = items.value
+    const map = new Map()
+    const keyless = []
+    for (let i = 0; i < _items.length; i++) {
+      const item = _items[i]
+      if (isPrimitive(item.value) || item.value === null) {
+        let values = map.get(item.value)
+        if (!values) {
+          values = []
+          map.set(item.value, values)
+        }
+        values.push(item)
+      } else {
+        keyless.push(item)
+      }
+    }
+    itemsMap.value = map
+    keylessItems.value = keyless
+  })
+
+  function transformIn (value: any[]): ListItem[] {
+    // Cache unrefed values outside the loop,
+    // proxy getters can be slow when you call them a billion times
+    const _value = toRaw(value)
+    const _items = itemsMap.value
+    const _allItems = items.value
+    const _keylessItems = keylessItems.value
     const _hasNullItem = hasNullItem.value
     const _returnObject = props.returnObject
-    const valueComparator = props.valueComparator
+    const hasValueComparator = !!props.valueComparator
+    const valueComparator = props.valueComparator || deepEqual
+    const _props = toRaw(props)
 
     const returnValue: ListItem[] = []
-    for (const v of value) {
+    main: for (const v of _value) {
       // When the model value is null, return an InternalItem
       // based on null only if null is one of the items
       if (!_hasNullItem && v === null) continue
@@ -113,13 +140,31 @@ export function useItems (props: ItemProps) {
       // String model value means value is a custom input value from combobox
       // Don't look up existing items if the model value is a string
       if (_returnObject && typeof v === 'string') {
-        returnValue.push(transformItem(props, v))
+        returnValue.push(transformItem(_props, v))
+        continue
+      }
+
+      // Fast path, items with primitive values and no
+      // custom valueComparator can use a constant-time
+      // map lookup instead of searching the items array
+      const fastItems = _items.get(v)
+
+      // Slow path, always use valueComparator.
+      // This is O(n^2) so we really don't want to
+      // do it for more than a couple hundred items.
+      if (hasValueComparator || !fastItems) {
+        for (const item of (hasValueComparator ? _allItems : _keylessItems)) {
+          if (valueComparator(v, item.value)) {
+            returnValue.push(item)
+            continue main
+          }
+        }
+        // Not an existing item, construct it from the model (#4000)
+        returnValue.push(transformItem(_props, v))
         continue
       }
 
-      returnValue.push(
-        _items.find(item => valueComparator(v, item.value)) || transformItem(props, v)
-      )
+      returnValue.push(...fastItems)
     }
 
     return returnValue
diff --git a/packages/vuetify/src/composables/nested/selectStrategies.ts b/packages/vuetify/src/composables/nested/selectStrategies.ts
index 5affb7e152b..9d9f90ede38 100644
--- a/packages/vuetify/src/composables/nested/selectStrategies.ts
+++ b/packages/vuetify/src/composables/nested/selectStrategies.ts
@@ -88,13 +88,11 @@ export const independentSingleSelectStrategy = (mandatory?: boolean): SelectStra
       return parentStrategy.select({ ...rest, id, selected: singleSelected })
     },
     in: (v, children, parents) => {
-      let map = new Map()
-
       if (v?.length) {
-        map = parentStrategy.in(v.slice(0, 1), children, parents)
+        return parentStrategy.in(v.slice(0, 1), children, parents)
       }
 
-      return map
+      return new Map()
     },
     out: (v, children, parents) => {
       return parentStrategy.out(v, children, parents)
@@ -188,7 +186,7 @@ export const classicSelectStrategy = (mandatory?: boolean): SelectStrategy => {
         map = strategy.select({
           id,
           value: true,
-          selected: new Map(map),
+          selected: map,
           children,
           parents,
         })
diff --git a/packages/vuetify/src/util/helpers.ts b/packages/vuetify/src/util/helpers.ts
index 01e719fde54..19a08a709e9 100644
--- a/packages/vuetify/src/util/helpers.ts
+++ b/packages/vuetify/src/util/helpers.ts
@@ -772,3 +772,8 @@ export function checkPrintable (e: KeyboardEvent) {
   const noModifier = !e.ctrlKey && !e.metaKey && !e.altKey
   return isPrintableChar && noModifier
 }
+
+export type Primitive = string | number | boolean | symbol | bigint
+export function isPrimitive (value: unknown): value is Primitive {
+  return typeof value === 'string' || typeof value === 'number' || typeof value === 'boolean' || typeof value === 'bigint'
+}