Giaches de Wert (also Jacques/Jaches de Wert, Giaches de Vuert; 1535 – 6 May 1596) was a Franco-Flemish composer of the late Renaissance, active in Italy. Intimately connected with the progressive musical center of Ferrara, he was one of the leaders in developing the style of the late Renaissance madrigal. He was one of the most influential of late sixteenth-century madrigal composers, particularly on Claudio Monteverdi, and his later music was formative on the development of music of the early Baroque era.