Marcus Caelius (c. March 45 BC – c. September AD 9) was the senior centurion (Primus pilus) in XVIII Roman Legion who was killed in the Battle of the Teutoburg Forest. He is known from his cenotaph, which was discovered in 1620 in Birten (now a part of Xanten), Germany. Caelius is depicted wearing his military uniform, with phalerae (a type of military decoration), armillae (a type of bracelet), and a corona civica (an award for saving a fellow citizen's life), while in his right hand, he holds a vitis (carried by all centurions). On either side of his image are his non-combatant servants, Privatus and Thiaminus, both of whom perished in the battle and were given the status of freedman post-humously by Caelius’ brother, Publius.

The tombstone's lower left corner is damaged, but enough survives to determine that the text below the image once read:

M[ARCO] CAELIO T[ITI] F[ILIO] LEM[ONIA TRIBV] BON[ONIA]

P[RIMVS] O[RDO] LEG[IONIS] XIIX ANN[ORVM] LIII S[EMISSIS]

[CE]CIDIT BELLO VARIANO OSSA

[HVC] INFERRE LICEBIT P[UBLIVS] CAELIVS T[ITI] F[ILIVS]

LEM[ONIA TRIBV] FRATER FECIT

English translation: