John Thirtle (baptized 22 June 1777 – 30 September 1839) was an English watercolour artist and frame-maker. Born in Norwich, where he lived for most of his life, he was a leading member of the Norwich School of painters.
Much of Thirtle's life is undocumented. After working as an apprentice to a London frame-maker, he returned to Norwich to establish his own frame-making business. During his career he also worked as a drawing-master, a printseller and a looking glass maker. He produced frames for paintings by several members of the Norwich School, including John Crome and John Sell Cotman. Throughout his working life he continued to paint. In 1812 he married Elizabeth Miles, the sister of Cotman's wife Ann. Thirtle suffered from tuberculosis during the last two decades of his life, and his worsening health reduced his artistic output up to his death in 1839. His unpublished manuscript Treatise on Watercolour was probably for his own use, and he exhibited fewer than 100 paintings. A member of the Norwich Society of Artists, he briefly served as its vice-president, but in 1816 was one of the artists who seceded from the Society to form a separate association, the Norfolk and Norwich Society of Artists, which dissolved after three years.
The majority of Thirtle's watercolours are of Norwich and the surrounding Norfolk countryside, many being riverside scenes. His style, influenced by Thomas Girtin, Crome and (to a lesser extent) Cotman, was technically accomplished. His earlier landscapes were painted with a restricted range of buffs, blues and grey-browns, but he later developed a brilliancy of colour, producing works that included angular block forms. The quality of several of his watercolours has deteriorated owing to the fading of the indigo pigment that he used extensively.
John Thirtle Old Lynndate not known