William (Bill) R. Siegel is an associate at Mayer Brown. Prior to joining Mayer Brown, Bill worked for an IP boutique law firm for over ten years. Bill has experience a wide range of intellectual property matters covering a variety of industries.

Bill’s trademark experience covers all aspects of trademark prosecution, including trademark clearance, registration, enforcement, and maintenance, for clients with global trademark portfolios. Bill counsels clients on availability of trademarks and reviews and prepares trademark searches and opinion letters. Bill also monitors trademark watch services and provides due diligence for potential oppositions.

Bill’s patent experience includes all aspects of patent prosecution, including patentability opinions, prosecution and maintenance. Bill also has experience defending patents in US Federal Courts and at the International Trade Commission.

Bill also has applied his trademark and patent experience to his transaction practice, which includes due diligence of intellectual property assets.


University of Illinois, BS

University of Illinois College of Law, JD, cum laude


  • Illinois


  • US Patent and Trademark Office