Bánk bán is an opera in 3 Acts by composer Ferenc Erkel. The work uses a Hungarian language libretto by Béni Egressy which is based on a stage play of the same name by József Katona. (Bán is ban in English, similar to a viceroy, a duke or palatine.) The main storyline is based on the assassination of Queen Gertrúd, wife of Andrew II in 1213. The opera was first performed at the Pesti Nemzeti Magyar Szinház, Budapest on 9 March 1861.

Setting: Hungary in the year 1213

King Endre II, the monarch of the country, is fighting abroad while Gertrúd, his queen, who is of Meranian birth, plays hostess to the leading members of the Court (in the first place foreigners) at prodigal feasts. Bán Bánk, the king's deputy, is touring the poverty-ridden country while Otto, the Queen's younger brother, is trying to seduce Bánk's beautiful wife Melinda. A group of angry Magyar nobles headed by Bán Petur are plotting a conspiracy against the queen, anxious for the fate of their homeland and the honour of Bánk's wife. Petur has sent for Bánk, hoping to recruit him for their cause. The Bán arrives, but is outraged that his old friend would dare threaten the throne. When Petur informs him of Otto's advances toward Melinda, however, Bánk promises that he shall attend their meeting.

Bánk is a village and municipality in the comitat of Nógrád, Hungary.

Coordinates: 47°55′28″N 19°10′31″E / 47.92444°N 19.17528°E / 47.92444; 19.17528