Mesopotamia (Greek: Μεσοποταμία) was the name of a Byzantine theme (a military-civilian province) located in what is today eastern Turkey.

The theme was formed probably between 899 and 911, when Emperor Leo VI (r. 886–912) appointed the former proconsul of the Province of Pontus, named Lucius, as its governor.

Manuel and his four sons were persuaded to cede their territory to the Byzantine Empire in exchange for titles and estates in other themes.

[3][4] Although Emperor Constantine VII Porphyrogennetos (r. 913–959) mentions that before its elevation to a theme, the region was an "unnamed kleisoura", there is evidence of much earlier administrative structures than that.

In the aftermath of the Battle of Manzikert in 1071, Emperor Michael VII Doukas (r. 1071–1078) tried to re-establish Byzantine authority, but the province fell to the Seljuk Turks.