Sylvanite is a census-designated place (CDP) in Lincoln County, Montana, United States. As of the 2020 census, Sylvanite had a population of 98.
The community is in Kootenai National Forest in northwestern Lincoln County, in the valley of the Yaak River, a south-flowing tributary of the Kootenai River. Yaak River Road (National Forest Road 92) runs through the valley, leading south to U.S. Route 2 in the Kootenai valley and northeast (upriver) to Yaak.
According to the U.S. Census Bureau, the Sylvanite CDP has an area of , all land.