John Dallachy (c. 1808 – 4 June 1871) was a curator of Melbourne Botanic Gardens and a plant collector. Dallachy was born in Elginshire, Scotland. He worked as a gardener for the Earl of Aberdeen and Kew Gardens. In 1847, he went to Ceylon to manage a coffee plantation. Sailing to Australia in 1848, he took up work as a gardener for Jonathan Were in Brighton, Victoria. He was an overseer and later a superintendent of the Melbourne Botanic Gardens from 1849 to 1857. Following the appointment of Ferdinand von Mueller as director, Dallachy continued as curator until 1861.