The Lady Evelyn River is a river in Nipissing, Sudbury and Timiskaming Districts, Ontario, Canada.

It lies mostly in Lady Evelyn-Smoothwater Provincial Park, and mostly within Timiskaming District, with the exception of a short portion of the South Branch at its most southern stretch, which lies in northeastern Sudbury District, and of the southernmost tip of Lady Evelyn Lake, which lies in northwestern Nipissing District.

Numerous waterfalls are found along the Lady Evelyn River, such as Frank's Falls.

The most impressive and highest is Helen Falls where water cascades from a height more than 25 m (82 ft).

This article related to a river in Northern Ontario, Canada is a stub.