St. Nicholas Cathedral, Orthodox cathedral in Kazan, Russia.

St. Nicholas Cathedral is a complex on Bauman Street made up of two connected churches: the brick, plastered Nikolо-Nizskaya church of 1885, a single-domed, single-apse hall church in eclectic style with classical elements, and the five-domed Pokrovskaya church. A five-tier bell tower and a chapel stand separately. The west facade on Bauman Street holds the main entrance, framed by rectangular niches.

A wooden church of St Nicholas stood here by 1565; at the end of the 17th century it was replaced by a stone church. The present Nicholas-Nizsky church was built in 1885 to designs funded by merchants including Shchetinkin, Zausaylov, Sveshnikov and Gorinov, whose names appear on a memorial plaque. Closed in 1930, it was handed to the Orthodox community in 1946 and consecrated as the Nicholas Cathedral on 22 March 1947.

The name Nikolsky distinguishes it from other Kazan churches dedicated to St. Nicholas; "Nizskaya" refers to its lower position relative to the nearby Church of St. Nicholas the Guest. Since 1947, March 22 is celebrated as the cathedral's patronal feast in honour of the Forty Martyrs of Sebaste, for whom a side altar was consecrated.

The complex stands on Bauman Street, the pedestrian axis of the old town, in the Vakhitovsky district. The entrance to the Nikolsky church faces the street, while a second door opens from the south side onto the church courtyard. The bell tower and the five-domed chapel of St. John the Warrior stand separately from the two linked churches.

The name "Nizskaya" distinguishes it from Kazan's other churches of St. Nicholas, some standing only tens of metres away; it referred to the site lying lower than the neighbouring Church of St. Nicholas Gostiny. A memorial plaque on the wall lists the merchants who funded the 1885 rebuilding, though only one of them, G. N. Gorinov, was a parishioner here.