Welser (vĕl`zər), German family of wealthy merchants and bankers at Augsburg. It reached the height of its prosperity under Bartholomäus Welser, 1488–1561, who had advanced large sums to Holy Roman Emperor Charles V. Unable to repay his debts, Charles granted (1528) virtual sovereignty over present Venezuela to his creditor, who sent out agents and had the territory explored. Charges (probably false) of oppressive administration brought a prolonged trial (1541–56); the Welser concession was revoked in 1556. A niece of Bartholomäus Welser, Philippine Welser, 1527–80, was famed for her beauty and erudition. She secretly married (1557) Archduke Ferdinand, second son of Holy Roman Emperor Ferdinand I.