Foss Peak, Mountain summit in Mount Rainier National Park, United States

Foss Peak is a summit in the Tatoosh Range located south of Mount Rainier within the national park boundaries. The peak sits at approximately 6,500 feet and connects to other peaks in this mountain chain that draw climbers and hikers throughout the year.

The summit was named after Thea Foss, a businesswoman who was active in Washington state during the early 1900s. The peak has been a recognized climbing destination in this mountain range for many decades.

The peak's name honours Thea Foss (1857–1927), who founded the Foss Maritime Company with her husband in 1889; the summit also carries the alternate name Manatee Mountain. Its slopes drain into tributaries of the Cowlitz River, and West Unicorn Peak lies 0.79 miles (1.27 km) to the southeast.

The best time to climb is from June through September when snow coverage is minimal and conditions are safest. Routes require proper gear and fitness levels, so visitors should prepare accordingly before attempting the ascent.

Foss Peak carries the alternate name Manatee Mountain, and its name honours Thea Foss (1857–1927), who founded the Foss Maritime Company with her husband in 1889. Its nearest higher neighbour is West Unicorn Peak, 0.79 miles (1.27 km) to the southeast.