St Just, known as St Just in Penwith, is a town and civil parish in the Penwith district of Cornwall, England, United Kingdom. It lies along the B3306 road which connects St Ives to the A30 road. The parish encompasses the town of St Just and the nearby settlements of Trewellard, Pendeen and Kelynack: it is bounded by the parishes of Morvah to the north-east, Sancreed and Madron to the east, St Buryan and Sennen to the south and by the sea in the west. The parish consists of 7,622 acres (3,085 ha) of land, 12 acres (4.9 ha) of water and 117 acres (47.3 ha) of foreshore. The town of St Just is the most westerly town in mainland Britain and is situated approximately 8 miles (13 km) west of Penzance along the A3071. St Just parish, which includes Pendeen and the surrounding area, has a population of 4,637. An electoral ward of the same name also exists: the population of this ward at the same census was 4,812.

Cornish is a Southwestern Brittonic language of the Celtic language family. Along with Welsh and Breton, Cornish is descended from the Common Brittonic language spoken throughout much of Great Britain before the English language came to dominate. For centuries, until it was pushed westwards by English, it was the main language of Cornwall, maintaining close links with its sister language Breton, with which it was mutually intelligible, perhaps even as long as Cornish continued to be spoken as a vernacular. Cornish continued to function as a common community language in parts of Cornwall until the mid 18th century, and there is some evidence for traditional speakers of the language persisting into the 19th century.