The Insubres or Insubri were a population settled in Insubria, in what is now Lombardy. They were the founders of Milan (Mediolanum). Though Celtic at the time of Roman conquest, they were most likely the result of the fusion of pre-existing Ligurian and Italic population strata with Gaulish tribes who had come from what is now southern France.

Together with the Boii, Lingones, Taurini, Gesati and other Gaulish groups, the Insubres were defeated in 224 or 225 BC by the Roman army led by consul Lucius Aemilius Papus at the Battle of Telamon. Two years later the Romans, backed by their Gaulish allies the Cenomani, reduced the only fortified place of the Insubres at Acerrae, and defeated them again at the Battle of Clastidium. After the defeat of the Gesati, they were compelled to accept the Roman occupation of Milan in 221 and forcible alliance with Rome, while the victors annexed much of their territory.

During the invasion of Hannibal of 218-217 BC, the Insubres rebelled in support of the Carthaginians. They supported the Carthaginians again in 200 BC, this time under Hamilcar. After several other clashes, they definitively allied with Rome in 194, maintaining some autonomy for their capital. In 89 BC they obtained Latin citizenship and, in 49 BC, Roman citizenship.

Romanization of the Insubres was probably quick, also due to the reported similarities of the Celtic and Latin languages; in a short span of time after the Roman conquest several literary figures emerged, like that of Caecilius Statius.

Insubria and Insubric language have been named after this people's name.

ca:Ínsubres cy:Insubres de:Insubrer et:Insuberid fr:Insubres it:Insubri nl:Insubres pl:Insubrowie ru:???????