The Archcathedral Basilica of the Assumption of the Blessed Virgin Mary and Saint Andrew (Polish: Bazylika archikatedralna Wniebowzięcia Najświętszej Maryi Panny i św. Andrzeja we Fromborku) in Frombork, Poland, is a Roman Catholic church located at the Cathedral Hill, by the Cathedral St. (ul. Katedralna 8) It was originally constructed from 1329 to 1388.

The basilica is one of Poland's official national Historic Monuments (Pomnik historii), as designated September 16, 1994 and tracked by the National Heritage Board of Poland.

The astronomer and mathematician Nicolaus Copernicus worked here as a canon (1512–16 and 1522–43). He wrote his epochal work, De revolutionibus orbium cœlestium in Frombork. Shortly after its 1543 publication, Copernicus died there and was buried in the cathedral where his grave was thought to have been found by archaeologists in 2005. This was subsequently confirmed in November 2008 by the publication of the results of DNA tests on fragments of bone and hair found on the skeleton; hair that matched two strands of hair which belonged to Copernicus and are currently located in Uppsala University.

In the northwest corner of the cathedral grounds is Copernicus' tower, and in the southwest corner an octagonal building with a square bell tower and a small planetarium and a Foucault's pendulum.

The city suffered destruction during the Polish–Swedish wars. Between 1626 and 1635 it was occupied by Gustavus Adolphus of Sweden who looted the cathedral and removed many cultural artefacts, including Copernicus' manuscripts to Sweden

The town and cathedral were badly damaged in World War II. After the war the cathedral was meticulously reconstructed.