St. Martin parish church, Structure of worship in Olten, Switzerland.

St. Martin is a parish church in Olten featuring three naves arranged in a columned basilica design with Romanesque Revival architectural elements. The structure omits a transept and demonstrates clean geometric lines throughout its interior layout.

The present St. Martin was built from 1908 to 1910 by St. Gallen architect August Hardegger in Neo-Romanesque style, next to the emergency church the remaining Roman Catholics had erected in 1876 after the 1875 founding of the Christian Catholic Church in the 1813 city church. The new parish church took the Martin patronage and has more seats than St. Ursen Cathedral in Solothurn. The former emergency church by Wilhelm Keller was converted into parish rooms and the Josefsaal.

The church is dedicated to Martin of Tours, a 4th-century bishop, and its name reflects that patronage. Since 1875 the 1813 city church has belonged to the Christian Catholic Church of Switzerland, whose founding national synod met there on 14 June 1875. The Roman Catholic parish built this church in 1908–1910 and gave it the same patronal name.

The church stands west of Olten's medieval town wall, on the site of the 1603 Holy Cross Chapel, a short walk from the old town and the Stadtturm. The main organ sits on three manuals and pedal, and a small choir organ of 881 pipes stands at the front of the left aisle.

The church has more seats than St. Ursen Cathedral in Solothurn. Its six bells, cast in 1909 by Rüetschi & Co. of Aarau, weigh 10,759 kg in total and are tuned to an extended Westminster motif; the four largest share the intervals of Big Ben. The largest bell, the 5,127 kg Trinity bell, hangs alone in the right tower.