The Byzantine Senate or Eastern Roman Senate (Greek: Σύγκλητος, Synklētos, or Γερουσία, Gerousia) was the continuation of the Roman Senate, established in the 4th century by Constantine I. It survived for centuries but was increasingly irrelevant until its eventual disappearance in the 13th century.

The Senate of the Eastern Roman Empire originally consisted of Roman senators who happened to live in the East, or those who wanted to move to Constantinople, and a few other bureaucrats who were appointed to the Senate. Constantine offered free land and grain to any Roman Senators who were willing to move to the East. When Constantine founded the Eastern Senate in Byzantium, it initially resembled the councils of important cities like Antioch rather than the Roman Senate. His son Constantius II raised it from the position of a municipal to that of an Imperial body but the Senate in Constantinople had essentially the same limited powers as the Senate in Rome. Constantius II increased the number of Senators to 2,000 by including his friends, courtiers, and various provincial officials.