Stein Valley Nlaka'pamux Heritage Park, Provincial park in Thompson-Nicola Regional District, Canada

Stein Valley Nlaka'pamux Heritage Park is a 1,072 km² backcountry provincial park about 20 km west of Lytton, British Columbia. It protects the entire Stein River watershed, from the river's source at Tundra Lake through Stein Lake down to the Fraser River, rising from 220 m to 2,954 m at Skihist Mountain. The valley contains U-shaped glacial valleys, cirques, tarns, three small glaciers, four larger lakes and over 500 km² of alpine meadows.

The valley faced threats from logging proposals during the 1980s until environmental advocates and the Lytton First Nation united to fight for its protection. In 1995, the area gained official protection status, establishing a management partnership between provincial authorities and the First Nation.

The name Stein comes from the Nlaka'pamux word Stagyn, meaning hidden place, because the valley is not visible from where the Stein River meets the Fraser. The Nlaka'pamux have used the valley for thousands of years as a travel route and for spiritual practice, including rock paintings and writings. A cooperative management agreement lets Lytton First Nation members continue harvesting resources for traditional, ceremonial or social activities.

The park is a backcountry area with no road access; entry is by ferry near Lytton, and the gravel approach roads are rough. There is no campground, though small cleared spots are prepared in some areas for tents. Campfires are banned year-round, and kayaking and rafting were suspended in June 2017 pending a review of their ecological impact.

The park straddles a climate boundary where hikers can walk from dry sagebrush forest into alpine tundra within a single day's journey. This range of environments packed into one valley creates an unusually layered ecosystem found nowhere else in the region.