Theodore the Studite (also known as Theodorus Studita, St. Theodore of Stoudios, and St. Theodore of Studium; 759–826) is a Byzantine Greek monk and abbot of the Stoudios monastery in Constantinople.

Theodore's letter, containing suggested monastery reform rules, is the first recorded stand against slavery.

He plays a major role in the revivals both of Byzantine monasticism and of classical literary genres in Byzantium.

He is known as a zealous opponent of iconoclasm, one of several conflicts that sets him at odds with both emperor and patriarch.