Chelmsford 123 is a British television situation comedy produced for Channel 4 by Hat Trick Productions.

The series is set in the British town of Chelmsford in the year AD 123 and concerned the power struggle between Roman governor Aulus Paulinus (Jimmy Mulville) and the British chieftain, Badvoc (Rory McGrath).

Aulus (probably a play on Aulus Platorius Nepos, the real governor of Roman Britain between 122 and 125) is a rather delicate Roman and is usually outwitted by the scheming Badvoc, who has not had a haircut for twenty-five years.

There are also appearances by many of the other regular "Hat Trick" actors, previously seen in shows such as Who Dares Wins.

Series 1 and 2 were released on DVD by Acorn Media UK on 15 September 2011.