Carstairs is a village in South Lanarkshire, Scotland. Carstairs is located 5 miles east of the county town of Lanark and the West Coast Main Line runs through the village. The village is served by Carstairs railway station, which is served by the Caledonian Sleeper to and from London Euston. Carstairs is best known as the location of the State Hospital. Carstairs is applied to the places Carstairs Village and the village of Carstairs Junction where the railway station is situated. The two places are two completely different villages divided by 1 mile of land, a parkland area and the railway line.

The West Coast Main Line (WCML) is one of the most important railway corridors in the United Kingdom, connecting the major cities of London and Glasgow with branches to Birmingham, Manchester, Liverpool and Edinburgh. It is one of the busiest mixed-traffic railway routes in Europe, carrying a mixture of intercity rail, regional rail, commuter rail and rail freight traffic. The core route of the WCML runs from London to Glasgow for 399 miles (642 km) and was opened from 1837 to 1881. With additional lines deviating to Northampton, Birmingham, Manchester, Liverpool and Edinburgh, this totals a route mileage of 700 miles (1,127 km). The Glasgow–Edinburgh via Carstairs line connects the WCML to Edinburgh. However, the main London–Edinburgh route is the East Coast Main Line. Several sections of the WCML form part of the suburban railway systems in London, Coventry, Birmingham, Manchester, Liverpool and Glasgow, with many more smaller commuter stations, as well as providing links to more rural towns.