Ossa, Mountain summit in Thessaly, Greece

Mount Ossa, also called Kissavos, is a mountain in the Larissa regional unit of Thessaly, Greece. Its highest summit, Profitis Ilias, reaches 1,978 metres and has been renamed Kostas Palamiotis. The mountain lies between Pelion to the south and Olympus to the north, separated from the latter by the Vale of Tempe. A valley divides it into two parts, called Megalo Farangi in the north and Megalo Rema in the south.

In ancient Greek mythology, the mountain appears in stories of giants attempting to stack it with other peaks. These tales highlight its importance in the ancient world's imagination.

The name Kissavos comes from the Serbian word kiša, meaning wet weather or rain, and came into use in the 11th century; the ancient name Ossa was revived in the 20th century. In Greek folklore Kissavos is the rival of Olympus in the klephtic song "Olympos and Kissavos", which praises the klephts of the 1821 Greek Revolution and which the critic Fauriel called the best klephtic song in his collection.

Hiking paths lead in multiple directions from the area, with access points from several nearby villages. The nearby Vale of Tempe serves as a natural landmark and separates this region from Mount Olympus.

The mountain has an unusual prominence of around 1,850 meters, meaning it stands noticeably distinct from all surrounding heights. This quality makes it a notable landmark in European geography.