St. Martin, Idstein, Cultural heritage church in Idstein, Germany.

St. Martin is a Catholic parish church in Idstein, built from 1963 to 1965 to a design by Johannes Krahn. Its single long nave ends in a semicircular choir, with a side chapel opening to the right. The walls are sandstone inside and out, the floor is Jura marble, and a free-standing concrete bell tower 42 m high carries four older bells.

A Gothic church dedicated to St. Martin replaced a Romanesque predecessor in 1330 and became the Protestant Unionskirche after the Reformation. Catholics regained the right to worship in 1806 and built the neo-Gothic Magdalenenkirche in 1888. That church was dynamited in 1963, and the present St. Martin, designed by Johannes Krahn, was consecrated on 5 June 1965.

The parish has long-standing ecumenical ties with Idstein's main Protestant church, the Unionskirche, with two regular joint services and concerts by combined choirs and ensembles. Church music, including a children's choir and groups playing historic instruments, has drawn attention in the Rhein-Main region.

The church is centrally located in Idstein's old town and easily reached on foot. Visitors should note that access to the interior may be limited to certain times or special occasions.

The free-standing 42-metre bell tower is made of exposed concrete and houses a memorial inside. It carries four older bells. The crucifixion group from the demolished 1888 Magdalenenkirche now stands in the sacrament chapel.