Reinagle was the son of an Hungarian musician living in Edinburgh. He came to London in 1763 to be articled to the painter Allan Ramsay, served an apprenticeship of seven years and then stayed with him as his assistant until Ramsay's death in 1784. During this time Reinagle is reported to have made more than ninety copies for Ramsay of his coronation portraits of George III and Queen Charlotte. Thereafter Reinagle specialised in animal painting but also painted landscapes and portraits. He exhibited at the Royal Academy from 1773 to 1827, becoming an Associate in 1787 and a full member in 1812. Italian subjects exhibited in 1799, 1800 and 1806 and a Portuguese one in 1816 suggest visits abroad. Reinagle also exhibited at the British Institution from 1806 to 1829. He died in London.
Reinagle married Jane Austin in 1771 and had eleven children. The eldest, the painter Ramsay Richard Reinagle (1775-1862, named after Allan Ramsay), is also represented in the Tate Gallery.
Denys Sutton, 'The Reinagles', Country Life, 1 December 1955, p.1264
Compact Edition of the Dictionary of National Biography, Oxford 1975, II, p.1753
Alastair Smart, Allan Ramsay: Painter, Essayist and Man of the Enlightenment, New Haven and London 1992, p.217