Jan Wellens de Cock was a Flemish painter and draftsman of the Northern Renaissance.
Little is known about his life and career. He was probably born in Leiden in Holland but settled in Antwerp. In 1506 Jan is recorded in the archives of the Guild of Saint Luke in Antwerp as having accepted an apprentice called 'Loduwyck'. It is unclear in which year Jan became a master. Jan Wellens de Cock could be identical with a certain 'Jan Van Leyen' who became a master in 1503–1504. On 6 August 1502 Jan Wellens de Cock married Clara, the daughter of Peter van Beeringen. Jan Wellens de Cock was probably identical to the 'Jan de Cock' that worked as a servant to the guild of 'Onze-Lieve-Vrouw Lof' for which he executed many commissions over the next few years. In 1507 de Cock was paid for painting angels and restoring the Holy Ghost at the altar of this guild in Antwerp Cathedral. These works were probably lost in the "beeldenstorm" of 1566. In 1511 the guild paid de Cock for cutting a woodblock for a print to use in the guild's procession. This is the only indication that de Cock, to whom several prints have been attributed, was indeed active as a block cutter.