Joshua Kirby (1716, Parham, Suffolk – 1774, Kew), often mistakenly called John Joshua Kirby, was an English 18th-century landscape painter, engraver, writer, draughtsman and architect famed for his publications and teaching on linear perspective based on Brook Taylor's mathematics.
Joshua was the second of five sons of topographer John Kirby. In young life he assisted his father in the preparation of his important Survey of Suffolk, which took the form of a volume (1735) entitled The Suffolk Traveller, an extensive gazetteer in which the parishes and towns, and the principal landowners, seats, advowsons, antiquities and industries of the two counties of West and East Suffolk were described, the text counterpart of John Kirby's County Map published in 1736. In 1739 Joshua married Sarah Bell, and his children Sarah (afterwards Mrs. Sarah Trimmer) and William soon followed. From an early age he was very studious, but, showing special aptitude as an artist, he settled down to work as a painter in Ipswich and accepted commissions. He was particularly interested in Perspective, and began to prepare a Treatise on the subject before discovering the work of Dr. Brook Taylor.
Making the friendship of Thomas Gainsborough he became interested in landscape, and with the encouragement of the antiquary Sir Joseph Ayloffe (who was developing materials for an extensive History of Suffolk) he prepared illustrations of ancient buildings and monuments in the county. From these Kirby published a set of twelve engraved by J. Ford in 1748, dedicating each to individual patrons, with a descriptive pamphlet. Kirby also prepared illustrations for the History of Dunwich by Thomas Gardner, published in 1754. In 1751 he issued proposals for a quarto volume on Brook Taylor's Perspective, made easy, both in Theory and Practice, to have a frontispiece by William Hogarth. By its title Kirby claimed less than his share of credit for its originality. The first edition appeared early in 1754. In this period he frequently visited London. He was admitted an honorary member of Hogarth's instructional project, the St Martin’s Lane Academy, where he lectured on perspective. By 1754 he had already received so much encouragement from distinguished artists that his first edition was over-subscribed, and, with 50 copper plates, a second issue was made the following year, price (to Subscribers) one guinea. Hogarth's Satire on False Perspective of 1753 was the frontispiece.