St. Mary's Church (Polish: Bazylika Mariacka, German: St. Marienkirche) is a Roman Catholic church and co-cathedral located in central Gdańsk, Poland. Completed in 1502 in the Brick Gothic architectural style, it is one of the world's largest brick churches and among the city's most important landmarks, known to its inhabitants as the Crown of Gdańsk (Polish: Korona Gdańska). Together with Oliwa Cathedral, it serves the Archdiocese of Gdańsk.
The groundbreaking ceremony took place in 1343, however, the construction of the present church began in 1379. St. Mary's is an aisled hall church with a transept; its exterior was largely influenced by other churches and temples built across cities or townships in proximity to the Baltic Sea that were part of the Hanseatic League. Between 1536 and 1572, St. Mary's Church was used for Catholic and Lutheran services simultaneously. Additionally, a domed side chapel in the Baroque fashion was erected for the Kings of Poland and Catholic worship in the late 17th century.