The Saint Nicholas Cathedral (Catedrala Sfântul Nicolae) is a Greek-Catholic church on Union Square in Oradea, Bihor County.
The cathedral was built between 1800 and 1810 on the site of a former church from the 1730s. The church was commissioned by Bishop Ignate Darabant and finished under Bishop Samuel Vulcan. It has a cross-shaped plan with a vaulted ceiling and a central dome, which is painted with biblical scenes.
In 1836, a fire destroyed the original tower that looked very similar to the one on the Moon Church on the opposite side of the square. In 1870, it was rebuilt with neo-Baroque and Byzantine styles, but another fire in 1907 caused significant damage again. Under Bishop Demetriu Radu a new spire was built on the tower, which was designed by the renowned architect Kálmán Rimanóczy jr.
In 1920, a Greek-Catholic school was built next to the church. In 1948, the communist regime banned the Greek-Catholic Church and the church lost its status as a cathedral to become a parish church of the Romanian Orthodox Church. In 2005, the church was returned to the Greek Catholic Diocese of Oradea. In 2019, a statue of Demetriu Radu, bishop between 1903 and 1920, was installed in front of the church.
