On 1 January 2015 the province was replaced by the Metropolitan City of Milan.

The province of Milan extended over the Po Valley and was bordered by the River Ticino to the west, and the River Adda to the east.

It was shaped by its waterways – river and canals that traverse it and sometimes border it, from the Lambro and Olona rivers to the numerous canals, like the Navigli Milanesi; these water runs link farmsteads and villages like Corneliano Bertario, the Castello Borromeo and ancient noble villas (such as the Inzago Villa near the Naviglio Martesana) to the Canale Villoresi, which is thought to be the longest man-made canal in Italy.

The Villoresi is the natural southern border of Brianza, an area in Lombardy noted for its mountains, lakes and plains.

Half of the province is agricultural and flood plain, and most of it is protected by reserves.