St. Martin Chapel, Romanesque chapel on Ufenau island, Lake Zurich, Switzerland

St. Martin Chapel, also called Reginlinde Chapel, is a towerless Romanesque building erected in 1141 on the hill of Ufnau island, on the foundations of a chapel founded around 950 by Reginlinde. Its side walls have high round-arched windows, while the recessed rectangular choir received a late Gothic tracery window. Abbot Berthold of Einsiedeln (1206–1213) renewed the portal, which bears his name.

A first, larger church on the hill probably dates from the 7th century. Around 950 Reginlinde founded a chapel whose foundations were reused in 1141 for the present towerless Romanesque building. Abbot Berthold of Einsiedeln (1206–1213) renewed the portal, which bears his name. St. Martin was originally the centre of a large parish reaching from Altendorf to Wädenswil and from Feldbach and Hombrechtikon to Erlenbach, administered from Pfäffikon on the mainland; with the building of St. Peter and Paul in the mid-10th century that parish function passed to it. Excavations took place in 1962, restoration 2007–2009.

The chapel is also called Reginlinde-Kapelle after Reginlinde, who founded a chapel here around 950; on Sechseläuten 2019 the Gesellschaft zu Fraumünster honoured her, and a plaque has stood by the chapel since June 2021. Inside, the choir arch shows busts of the wise and foolish virgins painted in the second quarter of the 16th century.

The chapel stands on Ufnau island in Lake Zurich and is reached by boat from the mainland; the island has no road link. From the landing point, a path climbs the hill to the building. Excavations in 1962 preceded the restoration carried out between 2007 and 2009.

The empty Baroque sarcophagus of Saint Adalrich stands at the rear of the nave; it was moved here from the former parish church of St. Peter and Paul after the 2009 restoration. Since June 2021 a plaque near the chapel honours Reginlinde, honoured by the Gesellschaft zu Fraumünster at the Sechseläuten in 2019.