Antoniterkapelle, Gothic church in Old Town, Mainz, Germany.

The Antoniterkapelle is a Gothic church in Mainz's Old Town featuring pointed arches, ribbed vaults, and stone construction typical of medieval religious buildings. The structure displays classic Gothic characteristics and is maintained as a protected cultural monument.

The chapel was built in 1330 when Mainz held considerable power as a free city and hosted numerous monasteries throughout its territory. This founding period coincided with an era of major church construction in the city.

The chapel is named after the Antonites, whose T-shaped cross still marks the portal. Since 1619 it belonged to the Poor Clares, whose founder, Saint Clare of Assisi, is depicted in a sculpture at the entrance from Klarastraße. Today the Diocese of Mainz uses the buildings for its church music institute, and a Portuguese-language Mass is celebrated almost every Sunday.

The chapel stands at the corner of Rosengasse and Klarastraße in Mainz's historic centre, with the entrance from Klarastraße marked by a sculpture of Saint Clare. The surrounding lanes are pedestrian, so it is reached on foot. Services are held in Portuguese almost every Sunday, and the chapel is often chosen for weddings, so weekday visits are less likely to coincide with a ceremony.

The chapel's vault holds the only surviving original medieval painting cycle in a Mainz church: restored murals of saints framed by painted tracery, uncovered and restored during the 1948 rebuilding after the 1942 fire. The portal still carries the order's T-shaped Antonite cross.