St. Mary's catholic church, Catholic parish church in Olten, Switzerland

St. Mary's is a Roman Catholic parish church on Engelbergstrasse in the Bifang district of Olten, built in 1952–1953 to plans by Basel architect Hermann Baur. An angled stairway leads up to the church, and the 42-metre bell tower with four bells stands apart like a campanile. A statue of the Virgin Mary by sculptor Paul Speck stands on the stairway.

St. Mary's was built from 1952 to 1953 to plans by Basel architect Hermann Baur, on the right bank of the Aare in the Bifang quarter. Its 42-metre campanile-like tower stands apart from the main building. The design echoes Baur's All Saints' Church in Basel (1948–1951), which has similar concrete light chambers and window walls.

The choir wall fresco and the concrete glass windows above the gallery were made by Ferdinand Gehr. His painting provoked strong rejection across German-speaking Switzerland and drew many curious visitors to Olten. The four bells, cast in 1952 by H. Rüetschi of Aarau, ring in the Gloria motif, the first four notes of the Easter sequence.

The church stands on Engelbergstrasse on the right bank of the Aare in the Bifang quarter, reached by an angled flight of steps. The 42-metre campanile-like tower with its four bells stands slightly apart from the main building. The Mary Chapel lies to the left of the chancel, set so that the view of the altar stays open.

The choir wall fresco by Ferdinand Gehr caused an outcry across German-speaking Switzerland when the church opened; after his abstract Wettingen painting, a bishop had refused to consecrate that church until it was covered. In Olten too a curtain was considered, yet the controversy drew crowds to the church.