Fort Joseph, Military fort in Mainz, Germany.

Fort Joseph, also called Josephsschanze, is a partially destroyed baroque outwork of Mainz's second fortification ring on the Linsenberg above the Zaybach valley. Its surviving pointed stone walls, where the flanks joined on both sides, are bounded today by Langebeckstraße and Czernyweg in the Oberstadt. The work had two lunettes placed one behind the other and a blockhouse covering the retreat.

The fort was constructed between 1713 and 1730 under architect Johann Maximilian von Welsch to defend Mainz following the end of French occupation. Its construction followed classical fortification principles and served as part of the regional defense strategy.

The name Josephsschanze refers to the schanze, a detached field fortification, dedicated to Saint Joseph. The fort was one of five detached forts built to reinforce Mainz after the Schönborn bastions of the first ring could be outranged by newer artillery. Its pointed stone walls now stand between Langebeckstraße and Czernyweg in the Oberstadt, near the university medical center.

The remains lie in Mainz-Oberstadt, bounded by Langebeckstraße and Czernyweg, on the Linsenberg height above the Zaybach valley near the university medical centre. Only the pointed stone walls of the fort's tip and its adjoining flanks survive, so the site is viewed from the surrounding streets rather than entered.

Fort Joseph had a Blockhaus covering the Retirade, a withdrawal point, and a large open area before its tip to sweep the so-called "heiliges Tal", a valley used for burials from Roman times into the 8th century. The fort's two lunettes lay one behind the other.