The Glasgow, Paisley, Kilmarnock and Ayr Railway (GPK&AR) was a railway in Scotland that provided train services between Glasgow, Kilmarnock and Ayr. It opened its first line, between Glasgow and Ayr, in stages from 1839 to 1840. The section between Glasgow and Paisley was made jointly with the Glasgow, Paisley and Greenock Railway. Later it built a line from Dalry via Kilmarnock to Cumnock, linking there with the Glasgow, Dumfries and Carlisle Railway, and together forming a through route from Glasgow to Carlisle. The two companies merged to form the Glasgow and South Western Railway.

The Glasgow, Paisley and Greenock Railway (GP&GR) was an early Scottish railway, opened in 1841, providing train services between Greenock and Glasgow. At the time the River Clyde was not accessible to sea-going ships, and the intention was to compete with river boats that brought goods to and from the city. In fact passenger traffic proved surprisingly buoyant, and connecting steamer services to island resorts in the Firth of Clyde provided a very great source of business.