Chatham Sound is a sound on the North Coast of British Columbia, Canada, bordering on Alaska, United States. It is located between the Dundas and Stephens Islands and the Tsimpsean Peninsula near Prince Rupert. It is part of the Inside Passage and extends from Portland Inlet in the north to Porcher Island in the south. It may have been named in 1788 by British Captain Charles Duncan after John Pitt, 2nd Earl of Chatham, who was First Lord of the Admiralty at that time.