Isabel Madeira (floruit 1546), was a Portuguese soldier, known for her participation in the defense of Portuguese Diu in India during the siege of 1546. Isabel Madeira alongside Isabel Fernandes, Catarina Lopes and Isabel Dias, was trained and commanded by D. João de Mascarenhas to work alongside the male soldiers to fortify and defense the city walls of Diu during the siege because of the small number of male soldiers available. She also worked as a nurse and tendered to her own spouse between her service on the city walls.