Pilėnai was a hill fort in the Grand Duchy of Lithuania. Its location is unknown and is subject to academic debates, but it is well known in the history of Lithuania due to its heroic defense against the Teutonic Order in 1336. Attacked by a large Teutonic force, the fortress, commanded by Duke Margiris, tried in vain to organize a defense against the larger and stronger invader. Losing hope, the defenders decided to burn their property and commit mass suicide to deprive the Order of prisoners and loot. This dramatic episode from the Lithuanian Crusade has caught the public imagination, inspired many works of fiction, and became a symbol of Lithuanian struggles and resistance.

Mass suicide is a form of suicide, occurring when a group of people simultaneously kill themselves.