diff --git a/objectivec/GPBUnknownField.h b/objectivec/GPBUnknownField.h
new file mode 100644
index 0000000..12d72a9
--- /dev/null
+++ b/objectivec/GPBUnknownField.h
@@ -0,0 +1,60 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#import <Foundation/Foundation.h>
+
+@class GPBCodedOutputStream;
+@class GPBUInt32Array;
+@class GPBUInt64Array;
+@class GPBUnknownFieldSet;
+
+NS_ASSUME_NONNULL_BEGIN
+
+@interface GPBUnknownField : NSObject<NSCopying>
+
+@property(nonatomic, readonly, assign) int32_t number;
+
+// Only one of these will be set.
+@property(nonatomic, readonly, strong) GPBUInt64Array *varintList;
+@property(nonatomic, readonly, strong) GPBUInt32Array *fixed32List;
+@property(nonatomic, readonly, strong) GPBUInt64Array *fixed64List;
+@property(nonatomic, readonly, strong) NSArray *lengthDelimitedList;  // NSData
+@property(nonatomic, readonly, strong) NSArray *groupList;  // GPBUnknownFieldSet
+
+// Only one of these should be used per Field.
+- (void)addVarint:(uint64_t)value;
+- (void)addFixed32:(uint32_t)value;
+- (void)addFixed64:(uint64_t)value;
+- (void)addLengthDelimited:(NSData *)value;
+- (void)addGroup:(GPBUnknownFieldSet *)value;
+
+@end
+
+NS_ASSUME_NONNULL_END