Atlin/A Téix'gi Aan Tlein Provincial Park, Provincial park in northwestern British Columbia, Canada

Atlin/Áa Tlein Téix'i Provincial Park is a 301,140-hectare back-country park in the Boundary Ranges of northwestern British Columbia, made up of two parts. Its eastern section carries the glaciers of the Juneau Icefield, chiefly the Llewellyn Glacier (71,140 hectares) and the Willison Glacier (10,165 hectares), and reaches the Alaska border. The southern third of Atlin Lake, 775 square kilometres and the province's largest natural freshwater body, lies inside the park, with Teresa Island and its 2,062-metre Birch Mountain.

The park was created in 1973 after BC Hydro proposed a tunnel diverting Atlin Lake water to the Taku River for hydropower. The new provincial NDP government also pledged over 600,000 hectares of new protected land, and Atlin was one of several parks established then. A 2011 land-use plan with the Taku River Tlingit now prohibits weir construction at the lake's outlet.

The name Atlin comes from Áa Tlein, the Tlingit phrase for "big body of water". The Taku River Tlingit hunted and fished here long before settlers arrived, and artifacts from nearly 40 excavated archaeological sites attest to that use. The 2011 land-use plan for the Atlin Lake area, completed with the Taku River Tlingit, bans weir construction and many other kinds of development.

Access is only by boat or floatplane since roads do not reach the park, and visitors must bring all necessary supplies as facilities are absent. Plan accordingly for the remote setting and lack of amenities.

Teresa Island, the largest island in the park, holds Birch Mountain at 2,062 m, described as the highest peak on an island in a freshwater lake. The Llewellyn Glacier, the park's largest at 71,140 hectares, is considered the source of the Yukon River.