The Croatian National Theatre in Zagreb (Croatian: Hrvatsko narodno kazalište u Zagrebu), commonly referred to as HNK Zagreb, is a theatre, opera and ballet house located in Zagreb.
The theatre evolved out of the first city theatre built in 1836 housed in the present-day Old City Hall. The theatre was first established as the Croatian National Theatre in 1860, and in 1861 it gained government support putting it on par with many other European national theatres. In 1870 an opera company was added to the theatre and in 1895 it moved to the new purpose-built building on Marshal Tito Square in Zagreb’s Lower Town, where it is based today.