The Battle of Mohi (Muhi) or Battle of the Sajó River (11 April 1241) is the main battle between the Mongol Empire and the Kingdom of Hungary during the Mongol invasion of Europe.

It takes place at Muhi, southwest of the Sajó River.

After the invasion, Hungary lies in ruins.

Nearly half of the inhabited places have been destroyed by the invading armies.

Around 15–25 percent of the population has been lost, mostly in lowland areas, especially in the Great Hungarian Plain, the southern reaches of the Hungarian plain in the area now called the Banat, and in southern Transylvania.