diff --git a/objectivec/GPBDescriptor.h b/objectivec/GPBDescriptor.h
new file mode 100644
index 0000000..360afe9
--- /dev/null
+++ b/objectivec/GPBDescriptor.h
@@ -0,0 +1,146 @@
+// 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>
+
+#import "GPBRuntimeTypes.h"
+
+@class GPBEnumDescriptor;
+@class GPBFieldDescriptor;
+@class GPBFieldOptions;
+@class GPBFileDescriptor;
+@class GPBOneofDescriptor;
+
+NS_ASSUME_NONNULL_BEGIN
+
+typedef NS_ENUM(NSInteger, GPBFileSyntax) {
+  GPBFileSyntaxUnknown = 0,
+  GPBFileSyntaxProto2 = 2,
+  GPBFileSyntaxProto3 = 3,
+};
+
+typedef NS_ENUM(NSInteger, GPBFieldType) {
+  GPBFieldTypeSingle,    // optional/required
+  GPBFieldTypeRepeated,  // repeated
+  GPBFieldTypeMap,       // map<K,V>
+};
+
+@interface GPBDescriptor : NSObject<NSCopying>
+
+@property(nonatomic, readonly, copy) NSString *name;
+@property(nonatomic, readonly, strong, nullable) NSArray *fields;
+@property(nonatomic, readonly, strong, nullable) NSArray *oneofs;
+@property(nonatomic, readonly, strong, nullable) NSArray *enums;
+@property(nonatomic, readonly, nullable) const GPBExtensionRange *extensionRanges;
+@property(nonatomic, readonly) NSUInteger extensionRangesCount;
+@property(nonatomic, readonly, assign) GPBFileDescriptor *file;
+
+@property(nonatomic, readonly, getter=isWireFormat) BOOL wireFormat;
+@property(nonatomic, readonly) Class messageClass;
+
+- (nullable GPBFieldDescriptor *)fieldWithNumber:(uint32_t)fieldNumber;
+- (nullable GPBFieldDescriptor *)fieldWithName:(NSString *)name;
+- (nullable GPBOneofDescriptor *)oneofWithName:(NSString *)name;
+- (nullable GPBEnumDescriptor *)enumWithName:(NSString *)name;
+
+@end
+
+@interface GPBFileDescriptor : NSObject
+
+@property(nonatomic, readonly, copy) NSString *package;
+@property(nonatomic, readonly) GPBFileSyntax syntax;
+
+@end
+
+@interface GPBOneofDescriptor : NSObject
+@property(nonatomic, readonly) NSString *name;
+@property(nonatomic, readonly) NSArray *fields;
+
+- (nullable GPBFieldDescriptor *)fieldWithNumber:(uint32_t)fieldNumber;
+- (nullable GPBFieldDescriptor *)fieldWithName:(NSString *)name;
+@end
+
+@interface GPBFieldDescriptor : NSObject
+
+@property(nonatomic, readonly, copy) NSString *name;
+@property(nonatomic, readonly) uint32_t number;
+@property(nonatomic, readonly) GPBDataType dataType;
+@property(nonatomic, readonly) BOOL hasDefaultValue;
+@property(nonatomic, readonly) GPBGenericValue defaultValue;
+@property(nonatomic, readonly, getter=isRequired) BOOL required;
+@property(nonatomic, readonly, getter=isOptional) BOOL optional;
+@property(nonatomic, readonly) GPBFieldType fieldType;
+// If it is a map, the value type is in -type.
+@property(nonatomic, readonly) GPBDataType mapKeyDataType;
+@property(nonatomic, readonly, getter=isPackable) BOOL packable;
+
+@property(nonatomic, readonly, assign, nullable) GPBOneofDescriptor *containingOneof;
+
+@property(nonatomic, readonly, nullable) GPBFieldOptions *fieldOptions;
+
+// Message properties
+@property(nonatomic, readonly, assign, nullable) Class msgClass;
+
+// Enum properties
+@property(nonatomic, readonly, strong, nullable) GPBEnumDescriptor *enumDescriptor;
+
+- (BOOL)isValidEnumValue:(int32_t)value;
+
+// For now, this will return nil if it doesn't know the name to use for
+// TextFormat.
+- (nullable NSString *)textFormatName;
+
+@end
+
+@interface GPBEnumDescriptor : NSObject
+
+@property(nonatomic, readonly, copy) NSString *name;
+@property(nonatomic, readonly) GPBEnumValidationFunc enumVerifier;
+
+- (nullable NSString *)enumNameForValue:(int32_t)number;
+- (BOOL)getValue:(nullable int32_t *)outValue forEnumName:(NSString *)name;
+
+- (nullable NSString *)textFormatNameForValue:(int32_t)number;
+
+@end
+
+@interface GPBExtensionDescriptor : NSObject<NSCopying>
+@property(nonatomic, readonly) uint32_t fieldNumber;
+@property(nonatomic, readonly) Class containingMessageClass;
+@property(nonatomic, readonly) GPBDataType dataType;
+@property(nonatomic, readonly, getter=isRepeated) BOOL repeated;
+@property(nonatomic, readonly, getter=isPackable) BOOL packable;
+@property(nonatomic, readonly, assign) Class msgClass;
+@property(nonatomic, readonly) NSString *singletonName;
+@property(nonatomic, readonly, strong, nullable) GPBEnumDescriptor *enumDescriptor;
+@property(nonatomic, readonly) id defaultValue;
+@end
+
+NS_ASSUME_NONNULL_END