Alt-katholische Kirche St. Theresia, Old Catholic church in Nordstrand, Germany.

The Alt-katholische Kirche St. Theresia is a brick hall church in Dutch Renaissance forms on the Osterdeich between the Alterkoog and Osterkoog polders. Its side walls and especially the gable front, which carries a roof turret with an octagonal lantern, are divided by numerous blind arches. Above the portal, the tower shaft bears the letters D O M, a Latin dedication to Deo Optimo Maximo.

The area was flooded in 1634, after which Duke Frederick III issued a decree in 1652 that brought Dutch experts to rebuild the island of Strand. This church emerged from that period of reconstruction and reflects Dutch influence on the area's architecture and settlement.

The church is also called Inseldom, after the letters D O M above the portal, which stand for the Latin dedication Deo Optimo Maximo. German sermons have been preached here only since the late 19th century; until 1920 the parish belonged to the Old Catholic Archdiocese of Utrecht. The altarpiece, a 17th-century Crucifixion, came from the earlier church.

The church stands on the Osterdeich between the Alterkoog and Osterkoog polders in the Süden district of Nordstrand, next to a thatched community centre. The brick gable front with its octagonal roof lantern faces the dike, so the building is easiest to find from the road along the polder edge.

In 1970 the church served as a film set for "Der Pfarrer von St. Pauli" starring Curd Jürgens. The brick facade and the octagonal lantern on the roof ridge appear in the production, which brought the small island church to cinema audiences.