Mrs. Theodore Atkinson Jr. is an oil-on-canvas portrait painting completed in 1765 by the American artist John Singleton Copley. It is now housed in the Crystal Bridges Museum of American Art.

John Singleton Copley was an Anglo-American painter, active in both colonial America and England. He was suspected to be born in Boston, Province of Massachusetts Bay, to Richard and Mary Singleton Copley, both Anglo-Irish. After becoming well-established as a portrait painter of the wealthy in colonial New England, he moved to London in 1774, never returning to America. In London, he met considerable success as a portraitist for the next two decades, and also painted a number of large history paintings, which were innovative in their readiness to depict modern subjects and modern dress. His later years were less successful, and he died heavily in debt. He was father of John Copley, 1st Baron Lyndhurst.