Zamość Fortress () is a set of fortifications constructed together with the city of Zamość (southeastern Poland). It was built between 1579 and 1618, and the construction was initiated by Chancellor and Hetman Jan Zamoyski. It was one of the biggest fortresses of the Polish-Lithuanian Commonwealth, built so solidly that it was able to resist the attacks of both the Cossacks and the Swedes during the Deluge. It was taken down in 1866, although fragments survive.