Mary, Countess of Falmouth and Dorset (1645 – 1679) was a British courtier and mistress of King Charles II. The King rewarded her with grants of land, including Somerset House, in the Strand, and a state pension. She was one of the Windsor Beauties painted by Sir Peter Lely. Her portrait by Lely was erroneously named "Elizabeth, Countess of Falmouth" and also as "Countess of Ossory" in some portrait prints and books in the 18th and 19th centuries, many of which were later reprinted, compounding the error.