Theodore the Studite ( ca. 758 - ca. 826 ) was a Christian monk widely known for his zealous opposition to iconoclasm, for his personal asceticism and monastic rule, and for the many liturgies he composed, particulary the Lenten Triodion which is still widely used in Eastern Orthodoxy.

He was born in Constantinople, and argued bravely in defense of icons in the capital of the Byzantine Empire during the emperor's opposition. At several later times in his life, he publicly criticised the reigning empire. At various times this earned him banishment and torture. Today he is widely regarded as a saint; his feast day is November 11.