The Lambro (Western Lombard: Lamber or Lambar) is a river of Lombardy, northern Italy, a left tributary of the Po.

The Lambro rises from the Monte San Primo, elevation 1,685 metres (5,528 ft), near the Ghisallo, in the province of Como, not far from Lake Como. After Magreglio it flows through the Vallassina and the comuni of Asso, Ponte Lambro and Erba, entering Lake Pusiano with the name of Lambrone. The Lambro passes through Brianza reaching Monza and crossing its famous park (where king Umberto I was assassinated by Gaetano Bresci) in two branches which join again before the river passes through the eastern part of Milan. At Melegnano it receives the waters of the Vettabbia and, at Sant'Angelo Lodigiano, those of its main tributary, the Lambro meridionale ("Southern Lambro"), almost doubling its discharge. The Lambro flows into the Po near Orio Litta.