Whistlejacket is an oil-on-canvas painting from about 1762 by the British artist George Stubbs showing the Marquess of Rockingham's racehorse approximately at life-size, rearing up against a plain background. The canvas is large, lacking any other content except some discreet shadows, and Stubbs has paid precise attention to the details of the horse's appearance. It has been described in The Independent as "a paradigm of the flawless beauty of an Arabian thoroughbred". The Fitzwilliam family, heirs of the childless Rockingham, retained the painting until 1997 when funding from the Heritage Lottery Fund allowed the National Gallery, London to acquire it for £11 million.
Stubbs was a specialist equine artist who in 1762 was invited by Rockingham to spend "some months" at Wentworth Woodhouse in Yorkshire, his main country house. Stubbs had painted many horse portraits, with and without human figures, but the heroic scale and lack of background of Whistlejacket are "unprecedented" in his work and equine portraits in general and "contemporaries were so astonished that a single horse should command a huge canvas that legends quickly developed" explaining why the painting was unfinished, none of which seem plausible or supported by the evidence to modern art historians. In fact Stubbs's earliest canvases on his visit in 1762 included a pair of much smaller paintings of groups of standing horses, one including Whistlejacket, in a horizontal format "like a classical frieze" with a similar honey beige background broken only by small shadows at the feet. It would seem likely that leaving the portraits without the usual landscape background was Rockingham's idea.
