diff --git a/Rules.md b/Rules.md
index a0d9960d..23d8d7ab 100644
--- a/Rules.md
+++ b/Rules.md
@@ -37,6 +37,7 @@
 * [modifierOrder](#modifierOrder)
 * [numberFormatting](#numberFormatting)
 * [opaqueGenericParameters](#opaqueGenericParameters)
+* [preferCountWhere](#preferCountWhere)
 * [preferForLoop](#preferForLoop)
 * [preferKeyPath](#preferKeyPath)
 * [redundantBackticks](#redundantBackticks)
@@ -1655,6 +1656,32 @@ Without this declaration, only functions will be reordered, while properties wil
 </details>
 <br/>
 
+## preferCountWhere
+
+Prefer `count(where:)` over `filter(_:).count`.
+
+<details>
+<summary>Examples</summary>
+
+```diff
+- planets.filter { !$0.moons.isEmpty }.count
++ planets.count(where: { !$0.moons.isEmpty })
+
+- planets.filter { planet in
+-     planet.moons.filter { moon in
+-         moon.hasAtmosphere
+-     }.count > 1
+- }.count
++ planets.count(where: { planet in
++     planet.moons.count(where: { moon in
++         moon.hasAtmosphere
++     }) > 1
++ })
+```
+
+</details>
+<br/>
+
 ## preferForLoop
 
 Convert functional `forEach` calls to for loops.
diff --git a/Sources/RuleRegistry.generated.swift b/Sources/RuleRegistry.generated.swift
index 4714e322..1d7f5e71 100644
--- a/Sources/RuleRegistry.generated.swift
+++ b/Sources/RuleRegistry.generated.swift
@@ -56,6 +56,7 @@ let ruleRegistry: [String: FormatRule] = [
     "numberFormatting": .numberFormatting,
     "opaqueGenericParameters": .opaqueGenericParameters,
     "organizeDeclarations": .organizeDeclarations,
+    "preferCountWhere": .preferCountWhere,
     "preferForLoop": .preferForLoop,
     "preferKeyPath": .preferKeyPath,
     "privateStateVariables": .privateStateVariables,
diff --git a/Sources/Rules/PreferCountWhere.swift b/Sources/Rules/PreferCountWhere.swift
new file mode 100644
index 00000000..9b25ad00
--- /dev/null
+++ b/Sources/Rules/PreferCountWhere.swift
@@ -0,0 +1,119 @@
+//
+//  PreferCountWhere.swift
+//  SwiftFormat
+//
+//  Created by Cal Stephens on 12/7/24.
+//  Copyright © 2024 Nick Lockwood. All rights reserved.
+//
+
+import Foundation
+
+public extension FormatRule {
+    static let preferCountWhere = FormatRule(
+        help: "Prefer `count(where:)` over `filter(_:).count`.")
+    { formatter in
+        // count(where:) was added in Swift 6.0
+        guard formatter.options.swiftVersion >= "6.0" else { return }
+
+        formatter.forEach(.identifier("filter")) { filterIndex, _ in
+            guard let nextIndex = formatter.index(of: .nonSpaceOrCommentOrLinebreak, after: filterIndex) else { return }
+
+            // Parse the `filter` call, which takes exactly one closure
+            // and is either `filter { ... }` or `filter({ ... })`
+            let openParen: Int?
+            let startOfClosure: Int
+            let endOfClosure: Int
+            let closeParen: Int?
+
+            if formatter.tokens[nextIndex] == .startOfScope("("),
+               let startOfClosureIndex = formatter.index(of: .nonSpaceOrCommentOrLinebreak, after: nextIndex),
+               formatter.tokens[startOfClosureIndex] == .startOfScope("{"),
+               let endOfClosureIndex = formatter.endOfScope(at: startOfClosureIndex),
+               let tokenAfterClosure = formatter.index(of: .nonSpaceOrCommentOrLinebreak, after: endOfClosureIndex),
+               formatter.tokens[tokenAfterClosure] == .endOfScope(")")
+            {
+                openParen = nextIndex
+                startOfClosure = startOfClosureIndex
+                endOfClosure = endOfClosureIndex
+                closeParen = tokenAfterClosure
+            }
+
+            else if formatter.tokens[nextIndex] == .startOfScope("{"),
+                    let endOfClosureIndex = formatter.endOfScope(at: nextIndex)
+            {
+                openParen = nil
+                startOfClosure = nextIndex
+                endOfClosure = endOfClosureIndex
+                closeParen = nil
+            }
+
+            else {
+                return
+            }
+
+            // Check if there's a `.count` property access after the filter call
+            guard let dotIndex = formatter.index(of: .nonSpaceOrCommentOrLinebreak, after: closeParen ?? endOfClosure),
+                  formatter.tokens[dotIndex] == .operator(".", .infix),
+                  let countIndex = formatter.index(of: .nonSpaceOrCommentOrLinebreak, after: dotIndex),
+                  formatter.tokens[countIndex] == .identifier("count")
+            else { return }
+
+            // Ensure the `.count` is a property access, not a method call.
+            if let tokenAfterCount = formatter.index(of: .nonSpaceOrCommentOrLinebreak, after: countIndex),
+               formatter.tokens[tokenAfterCount].isStartOfScope
+            { return }
+
+            // Remove the `.count` property access.
+            formatter.removeToken(at: countIndex)
+            formatter.removeToken(at: dotIndex)
+
+            // Replace the `filter(_:)` call with `count(where:)`.
+            // Since the `where` label provides semantic value,
+            // convert to the non-trailing-closure form.
+
+            // Replace `filter({ ... })` with `count(where: { ... })`.
+            if let openParen = openParen, let closeParen = closeParen {
+                formatter.replaceToken(at: filterIndex, with: .identifier("count"))
+
+                formatter.insert(
+                    [.identifier("where"), .delimiter(":"), .space(" ")],
+                    at: openParen + 1
+                )
+            }
+
+            // Replace `filter { ... }` with `count(where: { ... })`.
+            else {
+                formatter.insert(.endOfScope(")"), at: endOfClosure + 1)
+
+                formatter.insert(
+                    [.startOfScope("("), .identifier("where"), .delimiter(":"), .space(" ")],
+                    at: startOfClosure
+                )
+
+                if formatter.tokens[filterIndex + 1].isSpace {
+                    formatter.removeToken(at: filterIndex + 1)
+                }
+
+                formatter.replaceToken(at: filterIndex, with: .identifier("count"))
+            }
+        }
+    } examples: {
+        """
+        ```diff
+        - planets.filter { !$0.moons.isEmpty }.count
+        + planets.count(where: { !$0.moons.isEmpty })
+
+        - planets.filter { planet in
+        -     planet.moons.filter { moon in
+        -         moon.hasAtmosphere
+        -     }.count > 1
+        - }.count
+        + planets.count(where: { planet in
+        +     planet.moons.count(where: { moon in
+        +         moon.hasAtmosphere
+        +     }) > 1
+        + })
+        ```
+        """
+    }
+}
diff --git a/SwiftFormat.xcodeproj/project.pbxproj b/SwiftFormat.xcodeproj/project.pbxproj
index 9faedf7f..0653846c 100644
--- a/SwiftFormat.xcodeproj/project.pbxproj
+++ b/SwiftFormat.xcodeproj/project.pbxproj
@@ -631,6 +631,11 @@
 		2E9DE5082C95F9A1000FEDF8 /* FileMacro.swift in Sources */ = {isa = PBXBuildFile; fileRef = 2E9DE5052C95F9A1000FEDF8 /* FileMacro.swift */; };
 		2E9DE5092C95F9A1000FEDF8 /* FileMacro.swift in Sources */ = {isa = PBXBuildFile; fileRef = 2E9DE5052C95F9A1000FEDF8 /* FileMacro.swift */; };
 		2E9DE50F2C95FBB6000FEDF8 /* FileMacroTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 2E9DE50A2C95FB4F000FEDF8 /* FileMacroTests.swift */; };
+		2EA8C3702D04F51A00843B42 /* PreferCountWhere.swift in Sources */ = {isa = PBXBuildFile; fileRef = 2EA8C36F2D04F51A00843B42 /* PreferCountWhere.swift */; };
+		2EA8C3712D04F51A00843B42 /* PreferCountWhere.swift in Sources */ = {isa = PBXBuildFile; fileRef = 2EA8C36F2D04F51A00843B42 /* PreferCountWhere.swift */; };
+		2EA8C3722D04F51A00843B42 /* PreferCountWhere.swift in Sources */ = {isa = PBXBuildFile; fileRef = 2EA8C36F2D04F51A00843B42 /* PreferCountWhere.swift */; };
+		2EA8C3732D04F51A00843B42 /* PreferCountWhere.swift in Sources */ = {isa = PBXBuildFile; fileRef = 2EA8C36F2D04F51A00843B42 /* PreferCountWhere.swift */; };
+		2EA8C3752D05282600843B42 /* PreferCountWhereTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 2EA8C3742D05282600843B42 /* PreferCountWhereTests.swift */; };
 		2EDC9DDA2CCE9A7C0085DBE2 /* DeclarationV2.swift in Sources */ = {isa = PBXBuildFile; fileRef = 2EDC9DD92CCE9A7C0085DBE2 /* DeclarationV2.swift */; };
 		2EDC9DDB2CCE9A7C0085DBE2 /* DeclarationV2.swift in Sources */ = {isa = PBXBuildFile; fileRef = 2EDC9DD92CCE9A7C0085DBE2 /* DeclarationV2.swift */; };
 		2EDC9DDC2CCE9A7C0085DBE2 /* DeclarationV2.swift in Sources */ = {isa = PBXBuildFile; fileRef = 2EDC9DD92CCE9A7C0085DBE2 /* DeclarationV2.swift */; };
@@ -1022,6 +1027,8 @@
 		2E8DE6F72C57FEB30032BF25 /* WrapSingleLineCommentsTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = WrapSingleLineCommentsTests.swift; sourceTree = "<group>"; };
 		2E9DE5052C95F9A1000FEDF8 /* FileMacro.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = FileMacro.swift; sourceTree = "<group>"; };
 		2E9DE50A2C95FB4F000FEDF8 /* FileMacroTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = FileMacroTests.swift; sourceTree = "<group>"; };
+		2EA8C36F2D04F51A00843B42 /* PreferCountWhere.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = PreferCountWhere.swift; sourceTree = "<group>"; };
+		2EA8C3742D05282600843B42 /* PreferCountWhereTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = PreferCountWhereTests.swift; sourceTree = "<group>"; };
 		2EDC9DD92CCE9A7C0085DBE2 /* DeclarationV2.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = DeclarationV2.swift; sourceTree = "<group>"; };
 		2EDC9DDE2CCE9BC70085DBE2 /* DeclarationV2Tests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = DeclarationV2Tests.swift; sourceTree = "<group>"; };
 		2EF737512C5E881C00128F91 /* CodeOrganizationTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CodeOrganizationTests.swift; sourceTree = "<group>"; };
@@ -1267,6 +1274,7 @@
 				2E2BABAE2C57F6DD00590239 /* EmptyBraces.swift */,
 				580496D42C584E8F004B7DBF /* EmptyExtensions.swift */,
 				2E2BABD92C57F6DD00590239 /* EnumNamespaces.swift */,
+				ABC4BA2B2CB9B094002C6874 /* EnvironmentEntry.swift */,
 				2E2BABC72C57F6DD00590239 /* ExtensionAccessControl.swift */,
 				2E2BABC02C57F6DD00590239 /* FileHeader.swift */,
 				2E9DE5052C95F9A1000FEDF8 /* FileMacro.swift */,
@@ -1287,6 +1295,7 @@
 				2E2BABF62C57F6DD00590239 /* NumberFormatting.swift */,
 				2E2BABED2C57F6DD00590239 /* OpaqueGenericParameters.swift */,
 				2E2BABBF2C57F6DD00590239 /* OrganizeDeclarations.swift */,
+				2EA8C36F2D04F51A00843B42 /* PreferCountWhere.swift */,
 				2E2BABCE2C57F6DD00590239 /* PreferForLoop.swift */,
 				2E2BABDB2C57F6DD00590239 /* PreferKeyPath.swift */,
 				9BDB4F1C2C94773600C93995 /* PrivateStateVariables.swift */,
@@ -1356,7 +1365,6 @@
 				2E2BABBB2C57F6DD00590239 /* WrapSingleLineComments.swift */,
 				2E2BABDF2C57F6DD00590239 /* WrapSwitchCases.swift */,
 				2E2BABF92C57F6DD00590239 /* YodaConditions.swift */,
-				ABC4BA2B2CB9B094002C6874 /* EnvironmentEntry.swift */,
 			);
 			path = Rules;
 			sourceTree = "<group>";
@@ -1390,6 +1398,7 @@
 				2E8DE6B62C57FEB30032BF25 /* EmptyBracesTests.swift */,
 				012242D92CD355B000B96EF8 /* EmptyExtensionsTests.swift */,
 				2E8DE6972C57FEB30032BF25 /* EnumNamespacesTests.swift */,
+				ABC11AF72CC082D300556471 /* EnvironmentEntryTests.swift */,
 				2E8DE6992C57FEB30032BF25 /* ExtensionAccessControlTests.swift */,
 				2E8DE6962C57FEB30032BF25 /* FileHeaderTests.swift */,
 				2E9DE50A2C95FB4F000FEDF8 /* FileMacroTests.swift */,
@@ -1410,6 +1419,7 @@
 				2E8DE6B02C57FEB30032BF25 /* NumberFormattingTests.swift */,
 				2E8DE69E2C57FEB30032BF25 /* OpaqueGenericParametersTests.swift */,
 				2E8DE6E22C57FEB30032BF25 /* OrganizeDeclarationsTests.swift */,
+				2EA8C3742D05282600843B42 /* PreferCountWhereTests.swift */,
 				2E8DE6982C57FEB30032BF25 /* PreferForLoopTests.swift */,
 				2E8DE6BF2C57FEB30032BF25 /* PreferKeyPathTests.swift */,
 				9BDB4F1A2C94760000C93995 /* PrivateStateVariablesTests.swift */,
@@ -1476,7 +1486,6 @@
 				2E8DE6F12C57FEB30032BF25 /* WrapSwitchCasesTests.swift */,
 				2E8DE6A42C57FEB30032BF25 /* WrapTests.swift */,
 				2E8DE6AC2C57FEB30032BF25 /* YodaConditionsTests.swift */,
-				ABC11AF72CC082D300556471 /* EnvironmentEntryTests.swift */,
 			);
 			path = Rules;
 			sourceTree = "<group>";
@@ -1882,6 +1891,7 @@
 				2E2BADA32C57F6DD00590239 /* RedundantTypedThrows.swift in Sources */,
 				2E2BAD4B2C57F6DD00590239 /* RedundantVoidReturnType.swift in Sources */,
 				2E2BAC332C57F6DD00590239 /* Semicolons.swift in Sources */,
+				2EA8C3702D04F51A00843B42 /* PreferCountWhere.swift in Sources */,
 				2E2BAC0B2C57F6DD00590239 /* Indent.swift in Sources */,
 				2E2BACC32C57F6DD00590239 /* SpaceInsideBrackets.swift in Sources */,
 				2EDC9DDA2CCE9A7C0085DBE2 /* DeclarationV2.swift in Sources */,
@@ -2104,6 +2114,7 @@
 				2E8DE7252C57FEB30032BF25 /* BracesTests.swift in Sources */,
 				2E8DE74B2C57FEB30032BF25 /* LeadingDelimitersTests.swift in Sources */,
 				2E8DE7552C57FEB30032BF25 /* RedundantTypedThrowsTests.swift in Sources */,
+				2EA8C3752D05282600843B42 /* PreferCountWhereTests.swift in Sources */,
 				015CE8B12B448CCE00924504 /* SingularizeTests.swift in Sources */,
 				2E8DE7042C57FEB30032BF25 /* ExtensionAccessControlTests.swift in Sources */,
 				015F83FB2BF1448D0060A07E /* ReporterTests.swift in Sources */,
@@ -2233,6 +2244,7 @@
 				2E2BAC682C57F6DD00590239 /* LinebreakAtEndOfFile.swift in Sources */,
 				2E2BAC8C2C57F6DD00590239 /* SpaceInsideComments.swift in Sources */,
 				2E2BAC102C57F6DD00590239 /* WrapMultilineConditionalAssignment.swift in Sources */,
+				2EA8C3712D04F51A00843B42 /* PreferCountWhere.swift in Sources */,
 				2E2BACC02C57F6DD00590239 /* TypeSugar.swift in Sources */,
 				2E2BACEC2C57F6DD00590239 /* RedundantObjc.swift in Sources */,
 				2E2BACE02C57F6DD00590239 /* RedundantReturn.swift in Sources */,
@@ -2373,6 +2385,7 @@
 				01BBD85B21DAA2A700457380 /* Globs.swift in Sources */,
 				2E2BAD112C57F6DD00590239 /* RedundantProperty.swift in Sources */,
 				01A8320824EC7F7700A9D0EB /* FormattingHelpers.swift in Sources */,
+				2EA8C3722D04F51A00843B42 /* PreferCountWhere.swift in Sources */,
 				082D644B2CA4719E0072DA14 /* RedundantEquatable.swift in Sources */,
 				2E2BACFD2C57F6DD00590239 /* BlankLinesBetweenImports.swift in Sources */,
 				2E2BACF12C57F6DD00590239 /* ConditionalAssignment.swift in Sources */,
@@ -2522,6 +2535,7 @@
 				2E2BADB22C57F6DD00590239 /* RedundantType.swift in Sources */,
 				9028F7851DA4B435009FE5B4 /* Formatter.swift in Sources */,
 				2E2BAD122C57F6DD00590239 /* RedundantProperty.swift in Sources */,
+				2EA8C3732D04F51A00843B42 /* PreferCountWhere.swift in Sources */,
 				082D644D2CA4719E0072DA14 /* RedundantEquatable.swift in Sources */,
 				E487212A201E3DD50014845E /* RulesStore.swift in Sources */,
 				2E2BACFE2C57F6DD00590239 /* BlankLinesBetweenImports.swift in Sources */,
diff --git a/Tests/Rules/PreferCountWhereTests.swift b/Tests/Rules/PreferCountWhereTests.swift
new file mode 100644
index 00000000..c2b43362
--- /dev/null
+++ b/Tests/Rules/PreferCountWhereTests.swift
@@ -0,0 +1,78 @@
+//
+//  PreferCountWhereTests.swift
+//  SwiftFormatTests
+//
+//  Created by Cal Stephens on 12/7/24.
+//  Copyright © 2024 Nick Lockwood. All rights reserved.
+//
+
+import Foundation
+import XCTest
+@testable import SwiftFormat
+
+final class PreferCountWhereTests: XCTestCase {
+    func testConvertFilterToCountWhere() {
+        let input = """
+        planets.filter({ !$0.moons.isEmpty }).count
+        """
+
+        let output = """
+        planets.count(where: { !$0.moons.isEmpty })
+        """
+
+        let options = FormatOptions(swiftVersion: "6.0")
+        testFormatting(for: input, output, rule: .preferCountWhere, options: options)
+    }
+
+    func testConvertFilterTrailingClosureToCountWhere() {
+        let input = """
+        planets.filter { !$0.moons.isEmpty }.count
+        """
+
+        let output = """
+        planets.count(where: { !$0.moons.isEmpty })
+        """
+
+        let options = FormatOptions(swiftVersion: "6.0")
+        testFormatting(for: input, output, rule: .preferCountWhere, options: options)
+    }
+
+    func testConvertNestedFilter() {
+        let input = """
+        planets.filter { planet in
+            planet.moons.filter { moon in
+                moon.hasAtmosphere
+            }.count > 1
+        }.count
+        """
+
+        let output = """
+        planets.count(where: { planet in
+            planet.moons.count(where: { moon in
+                moon.hasAtmosphere
+            }) > 1
+        })
+        """
+
+        let options = FormatOptions(swiftVersion: "6.0")
+        testFormatting(for: input, output, rule: .preferCountWhere, options: options)
+    }
+
+    func testPreservesFilterBeforeSwift6() {
+        let input = """
+        planets.filter { !$0.moons.isEmpty }.count
+        """
+
+        let options = FormatOptions(swiftVersion: "5.10")
+        testFormatting(for: input, rule: .preferCountWhere, options: options)
+    }
+
+    func testPreservesCountMethod() {
+        let input = """
+        planets.filter { !$0.moons.isEmpty }.count(of: earth)
+        """
+
+        let options = FormatOptions(swiftVersion: "6.0")
+        testFormatting(for: input, rule: .preferCountWhere, options: options)
+    }
+}