Gaius Crastinus (c. 85 BC – 48 BC) was a soldier in Julius Caesar's 10th legion during his Gallic Wars. He had first joined either the 8th or 9th legion in 65 BC, when Pompey Magnus had first raised these two legions in Spain. He transferred over to the 10th legion as a junior-grade centurion in 61 BC when it was first formed, after being handpicked by Caesar. After joining the 10th legion, he commanded a Century. Crastinus fought throughout Caesar's Gallic campaigns, and was present at the Battle of Alesia, where he witnessed the surrender of the Gallic chieftain Vercingetorix to the forces of the Roman Republic. Early in the war, Crastinus commanded his unit as it repelled an attempted crossing of a river by the Helvetii. Crastinus, whom Caesar considered to be amongst his best soldiers, was promoted by Caesar to the rank of Primus Pilus, or "First File" Centurion. This rank was one of exceptional prestige, since centurions of this rank commanded the first ("primus"), and most important, century in a Legion. With this rank, Crastinus also would have outranked all other centurions in his legion, as it was the highest possible rank of any enlisted Roman soldier.