John Reinhard Weguelin RWS ROI was an English painter and illustrator, active from 1877 to after 1910. He specialized in figurative paintings with lush backgrounds, typically landscapes or garden scenes. Weguelin emulated the neo-classical style of Edward Poynter and Lawrence Alma-Tadema, painting subjects inspired by classical antiquity and mythology. He depicted scenes of everyday life in ancient Greece and Rome, as well as mythological subjects, with an emphasis on pastoral scenes. Weguelin also drew on folklore for inspiration, and painted numerous images of nymphs and mermaids.

Although his earliest work was in watercolour, all of Weguelin's important works from 1878 to 1892 were oil paintings. In order to supplement his income, he drew and painted illustrations for several books, most famously Macaulay's Lays of Ancient Rome. His subjects were similar to those of his contemporary, John William Waterhouse, who also specialized in painting the female figure against dramatic backgrounds, but unlike Waterhouse, many of Weguelin's subjects are nude or scantily-clad. Weguelin was particularly noted for his realistic use of light. Beginning in 1893, Weguelin devoted himself almost entirely to watercolour, and became a member of the Royal Watercolour Society. Weguelin's work was exhibited at the Royal Academy and a number of other important London galleries, and was highly regarded during his career. He was forgotten following the first World War, as his style of painting fell out of fashion, and he is best remembered as the painter of Lesbia, depicting the fabled muse of the Roman poet Catullus.