Gaudemunda Sophia of Lithuania (also Gaudimantė; c. 1260 – 1288 or 1313) was the daughter of Traidenis, Grand Duke of Lithuania (c. 1270–1282). In 1279, she married Duke of Masovia Bolesław II (c. 1254–1313) of the Piast dynasty. He was the son of Ziemowit I, Prince of Masovia, and Pereyaslava, daughter of Daniel of Galicia of the Rurik dynasty.
Her husband united the Duchy of Masovia and then divided it between their sons, who were: