The Markarfljót rises in the Rauðafossafjöll massif, east of the volcano Hekla. The main sources for the river are the glaciers Mýrdalsjökull and Eyjafjallajökull. It flows through narrow gorges in the mountainous area between the glaciers Tindfjallajökull and Torfajökull, then spreads in the wide sandur plains at Iceland's south coast, near Þórsmörk. The Markarfljót takes its course first north, then west of Þórsmörk and finally empties into the Atlantic west of Eyjafjallajökull.