Katholische Kirche St. Martin, Catholic church in Altdorf, Switzerland.

The Pfarrkirche St. Martin is a Roman Catholic parish church built 1602–1606 by Rocco Ruggia, the first early Baroque church in German-speaking Switzerland. It stands slightly above Altdorf on a spur of the Eggberge, oriented west-east, and turns its 56-metre-long south facade toward the village. The body is stepped in three parts: a portico before the entrance portal, the projecting side chapel, and the sacristy, separated by sandstone lisenes and a mezzanine band of small round windows.

The structure was built between 1602 and 1606 according to plans by architect Rocco Ruggia and was the first early baroque church in German-speaking Switzerland. This architecture significantly influenced church construction in the region afterward.

The parish is first documented through a seal of 1260 showing Saint Martin, and the dedication is recorded in writing from 1359. The church district also includes the St. Anna ossuary chapel to the south, the Ölberg chapel to the north and the cemetery. The parish in its present form dates from 1846.

The church stands slightly above the village centre on a spur of the steeply dropping Eggberge, aligned exactly west-east, with its 56-metre south facade turned toward the village. The main entrance is left of the projecting chapel block, under a vaulted porch; a second portal with a porch is on the west end. The north long side has no entrance.

During renovations from 1965 to 1971, archaeologists discovered four predecessor buildings on this site. The oldest one dated back to the third quarter of the 7th century.