The Schiehallion experiment was an 18th-century experiment to determine the mean density of the Earth. Funded by a grant from the Royal Society, it was conducted in the summer of 1774 around the Scottish mountain of Schiehallion, Perthshire. The experiment involved measuring the tiny deflection of the vertical due to the gravitational attraction of a nearby mountain. Schiehallion was considered the ideal location after a search for candidate mountains, thanks to its isolation and almost symmetrical shape.

Schiehallion is a prominent cone-shaped mountain in the Breadalbane region of the Scottish Highlands, in the county of Perthshire. It rises to 1,083 metres (3,553 ft) and is classed as a Munro. Schiehallion has a rich flora, interesting folklore and archaeology, and a unique place in scientific history for an 18th-century experiment in "weighing the Earth". It is near the centre of mainland Scotland. The mountain's popularity amongst walkers led to erosion on its footpath and extensive repairs were undertaken in 2001.