Brenta (anc. Medoacus Major), a river of northern Italy, rises in a small lake about 8 m. S. E. of Trent in Tyrol, flows E. by N. and then E. by S. to a point about 20 m. from its source, where it crosses the boundary of Italy, turns S. near Primolano, and follows a southern course as far as Bassano. Here it emerges from the deep mountain gorges through which it has thus far flowed, and passes S. and S. E. across the level country of the province of Venice. At Limena, and at a point about 6 m. E. of Padua, canals connect it with the Bacchiglione; and at Dolo, 9 m. E. of Padua, another canal runs S. and S. E. from the Brenta to Brondolo at the southern end of the Venetian lagoon. This last-named channel was cut to break the force of the current at the principal mouth of the river; for the Brenta, continuing its course, flows into the lagoon exactly opposite the city of Venice. But this was found insufficient, and a second canal parallel to the first was cut from La Mira, a few miles further east.

The main bed of the Brenta below La Mira was at the same time made into a canal with embankments and locks; this part of the river is called Brenta Morta, and forms the principal means for the transportation of freight between Venice and Padua. The whole length of the river is about 120 m.