Saint Adalbert church in Nasielsk, Catholic parish church in Nasielsk, Poland

Saint Adalbert Church in Nasielsk is an unplastered red-brick Gothic Revival basilica, built to Józef Pius Dziekoński's design. It has three naves on a Latin-cross plan with a transept and a five-sided apse, a five-storey tower against the facade and a small ridge turret at the crossing. Cross-rib, stellar and umbrella vaults cover the interior; the front portal carries an arcaded frieze and a ceramic mosaic of Our Lady of Częstochowa.

The present church was built between 1898 and 1901 (some sources say 1904 or 1905) in Gothic Revival style to a design by Józef Pius Dziekoński, replacing an older Gothic building demolished in 1898 during the tenure of parish priest Piotr Krasiński. It was consecrated on 22 May 1909 by Bishop Antoni Julian Nowowiejski. Russian artillery shelled it in 1914–1918, and in 1941 the occupiers turned it into a storehouse for Jewish furniture; Soviet and then German shelling damaged it again in 1945.

The parish belongs to the Nasielsk deanery of the Płock diocese. Inside, a side altar from 1965 holds Adrian Głębocki's 1863 painting of the Martyrdom of Saint Adalbert, the church's patron. The Stations of the Cross by Kazimierz Mastelski date from 1914, and the organ prospectus is Neo-Gothic.

The church stands in central Nasielsk at the coordinates 52.59230, 20.80300. It is an active parish church of the Płock diocese, so visits are best arranged outside Mass times. The building is a registered immovable monument, and modest dress is appropriate inside.

The 1941 occupiers turned the church into a storehouse for Jewish furniture, and parishioners could attend services only in the sacristy. During the First World War the sacristan and a master carpenter hid the 1911 eleven-voice organ from Russian artillery fire; it returned after repair in 1925.