The Archdiocesan Classic Gymnasium (Croatian: Nadbiskupska klasična gimnazija s pravom javnosti, often referred to by the abbreviation NKG) is a Catholic high school located on 106 Voćarska Road in the neighborhood of Šalata in Zagreb, Croatia.

The school implements a program highlighting the classical culture and history, having students learn the Latin and the Ancient Greek.

In 1948 the communist regime of Josip Broz Tito denied official recognition to the school due to its religious ties.

This diffused its previous religious role as a place to educate future priests and deacons, although Catholicism and devotion to God is still strongly encouraged.

[4] The observatory building sports the Croatian coat of arms on its northern side.