ephemeral river in Western Australia, rising north of Meekatharra on Peak Hill in the Robinson Ranges and fed by its tributaries, the Sandford and Roderick. It flows sporadically (chiefly in winter) west, south, and again west to enter the Indian Ocean at Kalbarri, north of Geraldton, after a course of 440 miles (710 km). The explorer George Grey reached the river in 1839 on a forced march from Shark Bay to the Swan River and named it for the British scientist Sir Roderick Murchison. Its estuarine mouth, blocked by reefs, is a good fishing ground. The North West Coastal Highway crosses the river at Galena.

In 1891 the stream gave its name to one of Australia's richest goldfields. The original find was followed by the East Murchison (1895) and Peak Hill (1897) fields. Some gold is still mined, and sheep are raised. Kalbarri serves tourists visiting Kalbarri National Park on the lower Murchison, where the river cuts a scenic gorge (the Loop) through the coastal range.