The Naviglio della Martesana is a canal in the Lombardy region, Northern Italy. Running from the Adda river, in the vicinity of Trezzo sull'Adda, to Milan, it was also known as Naviglio Piccolo. It is part of the system of navigli of the Milan area.
Approximately 38 kilometres long, with a substantial section covered over or infilled, its width varies between 9 and 18 metres, while the depth is between one and three metres.
Originally named Naviglio Piccolo, it subsequently changed to Martesana from the name of the county across which it runs.
Along the way it crosses the boundaries of the villages of Trezzo sull'Adda, Vaprio d'Adda, Cassano d'Adda, Inzago, Bellinzago Lombardo, Gessate, Gorgonzola, Bussero, Cassina de' Pecchi, Cernusco sul Naviglio and Vimodrone, and gives the name Martesana to all this area.
The canal enters Milan alongside Via Padova until Cassina de' Pomm: at the junction with Via Melchiorre Gioia it disappears underground following the route of Via Melchiorre Gioia itself southwards. In the past it would have passed through the Fossa dell'Incoronata and the Laghetto di San Marco to connect with the Fossa Interna.