When did Spartacus and the Roman gladiators rebel and nearly take over Italy?

That would be Spartacus and his gang. A deserter from the Roman army, Spartacus was sold as a slave and trained as a gladiator.

He escaped in 73 B.C. and gathered an army of 70,000 runaway slaves on Mount Vesuvius. They defeated five Roman armies and escaped to Cisalpine Gaul, where Spartacus intended to disband his armies and send them to their homes.

Instead, they thought it over and decided to stay in Italy and plunder the villages.

After two years, Spartacus was killed in battle, the insurrection ground to a halt, and a multitude of captured rebels were crucified as an example to us all.