diff --git a/CHANGELOG.md b/CHANGELOG.md
index 405e939bd..424f4465a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -19,6 +19,9 @@
   found issues.  
   [krin-san](https://github.com/krin-san)
   [#3177](https://github.com/realm/SwiftLint/pull/3177)
+* Add opt-in `ibinspectable_in_extension` rule to lint against `@IBInspectable`
+  properties in `extensions`  
+  [Keith Smiley](https://github.com/keith)
 
 * Add `computed_accessors_order` rule to validate the order of `get` and `set`
   accessors in computed properties and subscripts.  
diff --git a/Source/SwiftLintFramework/Models/MasterRuleList.swift b/Source/SwiftLintFramework/Models/MasterRuleList.swift
index 78e8bd657..09134193f 100644
--- a/Source/SwiftLintFramework/Models/MasterRuleList.swift
+++ b/Source/SwiftLintFramework/Models/MasterRuleList.swift
@@ -69,6 +69,7 @@ public let masterRuleList = RuleList(rules: [
     FunctionDefaultParameterAtEndRule.self,
     FunctionParameterCountRule.self,
     GenericTypeNameRule.self,
+    IBInspectableInExtensionRule.self,
     IdenticalOperandsRule.self,
     IdentifierNameRule.self,
     ImplicitGetterRule.self,
diff --git a/Source/SwiftLintFramework/Rules/Lint/IBInspectableInExtensionRule.swift b/Source/SwiftLintFramework/Rules/Lint/IBInspectableInExtensionRule.swift
new file mode 100644
index 000000000..972ae36d8
--- /dev/null
+++ b/Source/SwiftLintFramework/Rules/Lint/IBInspectableInExtensionRule.swift
@@ -0,0 +1,52 @@
+import SourceKittenFramework
+
+public struct IBInspectableInExtensionRule: ConfigurationProviderRule, OptInRule, AutomaticTestableRule {
+    public var configuration = SeverityConfiguration(.warning)
+
+    public init() {}
+
+    public static let description = RuleDescription(
+        identifier: "ibinspectable_in_extension",
+        name: "IBInspectable in Extension",
+        description: "Extensions shouldn't add @IBInspectable properties.",
+        kind: .lint,
+        nonTriggeringExamples: [
+            Example("""
+            class Foo {
+              @IBInspectable private var x: Int
+            }
+            """)
+        ],
+        triggeringExamples: [
+            Example("""
+            extension Foo {
+              @IBInspectable private var x: Int
+            }
+            """)
+        ]
+    )
+
+    public func validate(file: SwiftLintFile) -> [StyleViolation] {
+        let collector = NamespaceCollector(dictionary: file.structureDictionary)
+        let elements = collector.findAllElements(of: [.extension])
+
+        return elements
+            .flatMap { element in
+                return element.dictionary.substructure.compactMap { element -> ByteCount? in
+                    guard element.declarationKind == .varInstance,
+                        element.enclosedSwiftAttributes.contains(.ibinspectable),
+                        let offset = element.offset
+                    else {
+                        return nil
+                    }
+
+                    return offset
+                }
+            }
+            .map {
+                StyleViolation(ruleDescription: type(of: self).description,
+                               severity: configuration.severity,
+                               location: Location(file: file, byteOffset: $0))
+            }
+    }
+}
diff --git a/SwiftLint.xcodeproj/project.pbxproj b/SwiftLint.xcodeproj/project.pbxproj
index 186672171..e611ff400 100644
--- a/SwiftLint.xcodeproj/project.pbxproj
+++ b/SwiftLint.xcodeproj/project.pbxproj
@@ -247,6 +247,7 @@
 		C25EBBE521078DCE00E27603 /* Glob.swift in Sources */ = {isa = PBXBuildFile; fileRef = C25EBBE321078DC700E27603 /* Glob.swift */; };
 		C26330382073DAC500D7B4FD /* LowerACLThanParentRule.swift in Sources */ = {isa = PBXBuildFile; fileRef = C26330352073DAA200D7B4FD /* LowerACLThanParentRule.swift */; };
 		C28B2B3D2106DF730009A0FE /* PrefixedConstantRuleConfiguration.swift in Sources */ = {isa = PBXBuildFile; fileRef = C28B2B3B2106DF210009A0FE /* PrefixedConstantRuleConfiguration.swift */; };
+		C2A8D076243C0D0300642BC9 /* IBInspectableInExtensionRule.swift in Sources */ = {isa = PBXBuildFile; fileRef = C2A8D075243C0D0300642BC9 /* IBInspectableInExtensionRule.swift */; };
 		C2B3C1612106F78C00088928 /* ConfigurationAliasesTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = C2B3C15F2106F78100088928 /* ConfigurationAliasesTests.swift */; };
 		C328A2F71E6759AE00A9E4D7 /* ExplicitTypeInterfaceRule.swift in Sources */ = {isa = PBXBuildFile; fileRef = C328A2F51E67595500A9E4D7 /* ExplicitTypeInterfaceRule.swift */; };
 		C3D23F1D21E3A33700E9BD1B /* UnusedControlFlowLabelRule.swift in Sources */ = {isa = PBXBuildFile; fileRef = D4D7320C21E15ED4001C07D9 /* UnusedControlFlowLabelRule.swift */; };
@@ -765,6 +766,7 @@
 		C25EBBE321078DC700E27603 /* Glob.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Glob.swift; sourceTree = "<group>"; };
 		C26330352073DAA200D7B4FD /* LowerACLThanParentRule.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = LowerACLThanParentRule.swift; sourceTree = "<group>"; };
 		C28B2B3B2106DF210009A0FE /* PrefixedConstantRuleConfiguration.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = PrefixedConstantRuleConfiguration.swift; sourceTree = "<group>"; };
+		C2A8D075243C0D0300642BC9 /* IBInspectableInExtensionRule.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = IBInspectableInExtensionRule.swift; sourceTree = "<group>"; };
 		C2B3C15F2106F78100088928 /* ConfigurationAliasesTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ConfigurationAliasesTests.swift; sourceTree = "<group>"; };
 		C328A2F51E67595500A9E4D7 /* ExplicitTypeInterfaceRule.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = ExplicitTypeInterfaceRule.swift; sourceTree = "<group>"; };
 		C3DE5DAA1E7DF99B00761483 /* FatalErrorMessageRule.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = FatalErrorMessageRule.swift; sourceTree = "<group>"; };
@@ -1198,6 +1200,7 @@
 				62A3E95B209E078000547A86 /* EmptyXCTestMethodRule.swift */,
 				626B01B420A1735900D2C42F /* EmptyXCTestMethodRuleExamples.swift */,
 				7723A4DE23442D7100F38590 /* RawValueForCamelCasedCodableEnumRule.swift */,
+				C2A8D075243C0D0300642BC9 /* IBInspectableInExtensionRule.swift */,
 				D4E92D1E2137B4C9002EDD48 /* IdenticalOperandsRule.swift */,
 				D4441A27213279950020896F /* InertDeferRule.swift */,
 				C26330352073DAA200D7B4FD /* LowerACLThanParentRule.swift */,
@@ -2208,6 +2211,7 @@
 				C3D23F1D21E3A33700E9BD1B /* UnusedControlFlowLabelRule.swift in Sources */,
 				55CE0585231899100023BA72 /* ContainsOverRangeNilComparisonRule.swift in Sources */,
 				6C1D763221A4E69600DEF783 /* Request+DisableSourceKit.swift in Sources */,
+				C2A8D076243C0D0300642BC9 /* IBInspectableInExtensionRule.swift in Sources */,
 				47ACC8981E7DC74E0088EEB2 /* ImplicitlyUnwrappedOptionalConfiguration.swift in Sources */,
 				787CDE39208E7D41005F3D2F /* SwitchCaseAlignmentConfiguration.swift in Sources */,
 				D450D1DD21F199F700E60010 /* TrailingClosureConfiguration.swift in Sources */,
diff --git a/Tests/LinuxMain.swift b/Tests/LinuxMain.swift
index cbce0abeb..545dfdcb9 100644
--- a/Tests/LinuxMain.swift
+++ b/Tests/LinuxMain.swift
@@ -664,6 +664,12 @@ extension GlobTests {
     ]
 }
 
+extension IBInspectableInExtensionRuleTests {
+    static var allTests: [(String, (IBInspectableInExtensionRuleTests) -> () throws -> Void)] = [
+        ("testWithDefaultConfiguration", testWithDefaultConfiguration)
+    ]
+}
+
 extension IdenticalOperandsRuleTests {
     static var allTests: [(String, (IdenticalOperandsRuleTests) -> () throws -> Void)] = [
         ("testWithDefaultConfiguration", testWithDefaultConfiguration)
@@ -1761,6 +1767,7 @@ XCTMain([
     testCase(FunctionParameterCountRuleTests.allTests),
     testCase(GenericTypeNameRuleTests.allTests),
     testCase(GlobTests.allTests),
+    testCase(IBInspectableInExtensionRuleTests.allTests),
     testCase(IdenticalOperandsRuleTests.allTests),
     testCase(IdentifierNameRuleTests.allTests),
     testCase(ImplicitGetterRuleTests.allTests),
diff --git a/Tests/SwiftLintFrameworkTests/AutomaticRuleTests.generated.swift b/Tests/SwiftLintFrameworkTests/AutomaticRuleTests.generated.swift
index b24e9b225..198c53ae7 100644
--- a/Tests/SwiftLintFrameworkTests/AutomaticRuleTests.generated.swift
+++ b/Tests/SwiftLintFrameworkTests/AutomaticRuleTests.generated.swift
@@ -264,6 +264,12 @@ class FunctionDefaultParameterAtEndRuleTests: XCTestCase {
     }
 }
 
+class IBInspectableInExtensionRuleTests: XCTestCase {
+    func testWithDefaultConfiguration() {
+        verifyRule(IBInspectableInExtensionRule.description)
+    }
+}
+
 class IdenticalOperandsRuleTests: XCTestCase {
     func testWithDefaultConfiguration() {
         verifyRule(IdenticalOperandsRule.description)