Thomas Girtin (18 February 1775 – 9 November 1802) was an English watercolourist and etcher. A friend and rival of J. M. W. Turner, Girtin played a key role in establishing watercolour as a reputable art form.

Girtin’s early landscapes are akin to 18th-century topographical sketches, but in later years he developed a bolder, more spacious, romantic style, which had a lasting influence on English painting.

The scenery of the north encouraged him to create a new watercolour palette of warm browns, slate greys, indigo and purple. He abandoned the practice of undershadowing in grey wash and then adding pastel patches of colour, in favour of broad washes of strong colour, and experimented with the use of pen, brown ink and varnish to add richer tones.

Girtin’s early death reportedly caused Turner to remark, “Had Tom Girtin lived I should have starved.” His most celebrated work, much admired by Turner, was The White House at Chelsea (1800).