Marfa Boretskaya, also known as Martha the Mayoress (Russian: Марфа Посадница - Marfa Posadnitsa), was the wife of Isaac Boretsky, Novgorod's posadnik in 1438–1439 and again in 1453. According to legend and historical tradition, she led the republic's struggle against Muscovy between her husband's death and the city's eventual annexation by Ivan III of Russia in 1478.