A dunam (Ottoman Turkish, Arabic: دونم; Turkish: dönüm; Hebrew: דונם), also known as a donum or dunum and as the old, Turkish, or Ottoman stremma, was the Ottoman unit of area equivalent to the Greek stremma or English acre, representing the amount of land that could be ploughed by a team of oxen in a day. The legal definition was "forty standard paces in length and breadth", but its actual area varied considerably from place to place, from a little more than 900 square metres (9,700 sq ft) in Ottoman Palestine to around 2,500 square metres (27,000 sq ft) in Iraq.

The unit is still in use in many areas previously ruled by the Ottomans, although the new or metric dunam has been redefined as exactly one decare (1,000 square metres (11,000 sq ft)), which is 1/10 hectare (1/10 × 10,000 square metres (110,000 sq ft)), like the modern Greek royal stremma.