William 'Spread Eagle' Grinly (also Grinley, Grindley or Grindlay)[a] (1748 – 1827) was a British soldier, merchant, and mariner during the 18th and 19th centuries, known for his often distinctive dress and flamboyant character.

His father and all three of his brothers were shipowners and shipmasters, and as a young man he travelled extensively as part of the family merchant shipping business, including going supercargo to Holland, France, Spain, Russia, and America.

[2][6] In the late 18th century, he was aboard the Isabella when it was captured on its homeward journey, and the entire ship's company robbed and marooned, with Grinly being stripped of all his possessions apart from his watch.

He established Anderson & Grinly,[1] a mercantile firm initially based in Bo'ness and Leith, but operations expanded across southern Scotland to include areas of the southwest coast.

However, when his operations in Bo'ness ultimately proved unsuccessful, he travelled to Ireland to establish a new line of enterprise and support the founding of various Protestant stranger churches.

[1][7] For several years after returning to Leith, Grinly operated a successful shipping business, but as a result of over speculation in maritime underwriting he lost the majority of his wealth.

[1] However, undeterred by his misfortunes, he then again reentered the world of commerce as a ship broker, merchant, and auctioneer, based in Tolbooth Wynd, Leith and amassed a considerable fortune enabling him to retire entirely from business.

[2][3] All throughout his life, Grinly was a committed Protestant, being an Elder of South Leith Parish Church for around 30 years and a close friend of William Robertson.

He was generally held in esteem, although his sarcastic humour was sometimes felt to be "biting rude", and, as with most other persons of his calling, excess of modesty could not be enumerated among his defects.

"[1] – John Kay (1742 – 1826) It was during one of his visits to Edinburgh that the Scottish caricaturist and engraver John Kay, sketched the 'Spread Eagle' and entered it into his A Series of Original Portraits and Caricature Etchings published in 1838,[1] accompanied by an extensive biographical profile, and where it featured alongside other prominent individuals of the day, including Adam Smith, Thomas Jefferson, Henry Dundas, 1st Viscount Melville and others.

"– Stated while stood atop a pile of wooden logs on the shore of Leith port, in response to a group of porters in his employment who suggested 'The Doctor',[c] another gentleman afforded one of Mr McLean's soubriquets, was more handsome than he.

"– An argument with a wealthy tradesman from Edinburgh, who in a violent temper, upon seeing a choice article of his sold to a rival for a low price, challenged Grinly as auctioneer to a duel.

Torn between the juror's fine or the loss of the sale, at the opening of proceedings Grinly immediately feigned sudden urgent illness and requested to leave, which when granted by the judge allowed him to avoid both.