St. Mark's Square (Croatian: Trg svetog Marka) is a square located in the old part of Zagreb, Croatia.

In the center of square is located St. Mark's Church. The square also sports important governmental buildings: Banski dvori (the seat of the Government of Croatia), Croatian Parliament (Croatian: Hrvatski sabor) and Constitutional Court of Croatia. On the corner of St. Mark's Square and the Street of Ćiril and Metod is the Old City Hall, where the Zagreb City Council held its sessions.

In 2006 the square has undergone through renovation project. Since August 2005, the Government forbid any form of protests on St. Mark's square which caused many controversies in Croatian's "civil society". This ban was partially lifted in 2012.