Christian catholic town church, Catholic church building in Olten, Switzerland.

Stadtkirche St. Martin is a Neoclassical church built from 1806 to 1813 to plans by Blasius Balteschwiler, replacing the old St. Martin's church of which only the city tower remains. Its two towers look like masonry but are timber frames clad in sheet metal, a deception noted by former city archivist Martin Eduard Fischer. Inside, a Kuhn organ of 1879 with 38 registers stands nearly in its original state.

Built from 1806 to 1813 to plans by architect Blasius Balteschwiler, the church replaced the old St. Martin's Church, of which only the city tower remains. It served as Olten's Roman Catholic town church until the First Vatican Council of 1870 and the Swiss Kulturkampf. On 14 June 1875 the founding National Synod of the Christian Catholic Church of Switzerland met here.

The church holds a 1879 Kuhn organ with 38 stops on three manuals and pedal, restored in 1983 and 2019 and nearly in its original state. Until the last renovation its upper part bore the gilt inscription GLORIA IN EXCELSIS DFO, the misspelling DFO for DEO corrected during the organ restoration. Since 2021 a small Italian choir organ by Vittorio Ramina, a 2002 copy of an 18th-century instrument, stands in the choir on the left gallery.

Since 2019 the congregation's services have been concentrated in this church, so it is the regular place of worship of the Christian Catholic parish of the Olten region. The building stands in the town centre, near the old town tower that survives from the previous church. Visitors should check the parish's current service times before planning a visit.

The two towers are not stone: Niklaus Purtschert's 1809 design was built as a timber frame with metal sheeting, painted to imitate masonry. The former city archivist Martin Eduard Fischer noted that they disguise the actual construction. In 1899 the Oltner Tagblatt reported a proposal to rebuild them properly once the ownership question was settled.