Constantine I Tich Asen was between the years 1258 and 1277 Tsar of the Second Bulgarian Empire. He became Tsar after the murder of Koloman and the defeat of Mico in the Bulgarian civil war of 1256-57. He married the Nicean Princess Eirine Laskarina and later Maria Palaiologina. Both wives influenced his foreign affairs. The internal politics were dominated by the disputes among the boyars. He died in a battle against the rebells commanded by Ivajlos.