thumb|right|Gold multiple of Constantine, minted in Ticinum, 313|alt=Full-view image of the coin
Ticinum (the modern Pavia) was an ancient city of Gallia Transpadana, founded on the banks of the river of the same name (now the Ticino) a little way above its confluence with the Padus (Po).
It was said by Pliny the Elder to have been founded by the Laevi and Marici, two Ligurian tribes, while Ptolemy attributes it to the Insubres.
Its importance in Roman times was due to the extension of the Via Aemilia from Ariminum (Rimini) to the Padus (or Po) (187 BC), which it crossed at Placentia (Piacenza) and there forked, one branch going to Mediolanum (Milan) and the other to Ticinum, and thence to Laumellum where it divided once more, one branch going to Vercellae, and thence to Eporedia and Augusta Praetoria; and the other to Valentia, and thence to Augusta Taurinorum (Turin) or to Pollentia. Ticinum was the site of a mint, transferred from Mediolanum by Aurelian in 275, which remained active until closed by Constantine the Great in 326.
The city was pillaged by Attila in 452 and by Odoacer in 476, but rose to importance as a military centre in the Gothic period. At Dertona and here the grain stores of Liguria were placed, and Theodoric the Great constructed a palace, baths and amphitheatre and new town walls; while an inscription of Athalaric relating to repairs of seats in the amphitheatre is preserved (529). Boethius wrote De consolatione philosophiae while imprisoned at Ticinum before his execution in late 525 or early 526. From this point, too, navigation on the Padus seems to have begun. Narses recovered it for the Eastern Empire, but after a long siege, the garrison had to surrender to the Lombards in 572. Cornelius Nepos, the biographer, appears to have been a native of Ticinum. Of Roman remains little is preserved; there is, for example, no sufficient proof that the cathedral rests upon an ancient temple of Cybele though the regular ground plan of the central portion, a square of some 1150 yards, betrays its Roman origin, and it may have sprung from a military camp. This is not unnatural, for Pavia was never totally destroyed; even the fire of 1004 can only have damaged parts of the city, and the plan of Pavia remained as it was. Its gates were possibly preserved until early in the 8th century.