Näsijärvi (Finnish: [ˈnæsiˌjærʋi]) is a lake 95 metres (312 ft) above sea level, in the Pirkanmaa region of southern Finland.

At the end of Aitolahti, it expands into a small Niihamanselkä, from which Olkahistenlahti diverges to the southeast and Merjanlahti and Laalahti to the northeast.

In the case of the islands, a wide headland protrudes from the east towards the lake, the southern tip of which is called Paavolanniemi.

There is a small, rocky island upon which a lighthouse, called Siilinkari [fi], is located; it is the most popular walking destination on the lake.

In the north Näsijärvi has a wide catchment area that includes among others the lakes Ruovesi, Kuorevesi, Keurusselkä, Tarjanne, Pihlajavesi, Toisvesi and Ähtärinjärvi.