Highland Railway Strath Class

The Highland Railway Strath Class was a series of inside-cylinder 4-4-0 express passenger locomotives designed by David Jones and built from 1892, named after the broad Highland valleys — strath being the Gaelic word for a wide river valley — that the Highland Railway served on its routes through the Scottish Highlands. The Strath Class was Jones's express passenger type of the early 1890s, a development of his Bruce Class that incorporated a larger boiler and detail improvements to address the growing weight and speed demands of the Highland Railway's express passenger services.

The Strath Class retained Jones's established 4-4-0 formula: inside cylinders, Westinghouse air brakes, 6 ft 3 in coupled driving wheels consistent with the Bruce and Baron classes, and the generous boiler proportions that Jones favoured for sustained steaming on the long Highland main-line distances. Named after Highland straths including Strathcarron, Strathdearn, Strathnairn, Strathpeffer, Strathrannoch, and others, the class gave reliable service on the Highland Railway's principal express duties through the 1890s before the Loch Class 4-4-0 took over the top express work from 1896.

The Strath Class continued on secondary express and semi-fast duties alongside the Loch Class until the introduction of the Castle Class 4-6-0 from 1900 displaced them further. All were withdrawn before the end of the LMS era. None was preserved.