Pine Hill Ecological Reserve, Protected nature area in El Dorado County, California, US.

Pine Hill Ecological Reserve covers 403 acres (1.63 km2) east of Folsom Lake in El Dorado County, California. It is the centrally located, state-owned unit of the five-unit Pine Hill Preserve and protects rare plants on gabbro-derived soil. Its landscape includes the 2,031-foot summit of Pine Hill, with ridgelines running northeast, west and south, and a gated road to a fire lookout.

Preservation began in 1977 when surplus California Department of Forestry land around Pine Hill was slated for disposal. The California Native Plant Society and other groups pushed for protection, and in May 1979 the summit became a 320-acre state ecological reserve. Later additions of 40 acres in 1991 and 43 acres in 2002 and 2004 brought the reserve to 403 acres.

The reserve takes its name from Pine Hill, whose 619-metre summit holds a fire lookout run by the California Department of Forestry. The rare plants grow on red gabbro-derived soil of the Rescue series, and four of the eight species are known only from the Pine Hill area.

Access is limited to guided tours because the rare plants are fragile and the reserve is almost entirely surrounded by private property. Naturalist-led tours are run by the Bureau of Land Management and are capped at 30 people. A gated, closed road leads to the 2,031-foot summit of Pine Hill, where a fire lookout stands.

Four of the eight rare plants protected by the Pine Hill Preserve grow only in the Pine Hill area and nowhere else on Earth. The reserve's gabbro soil, formed about 175 million years ago in the late Jurassic, is red, sandy loam rich in iron and magnesium.