James Edgar Dandy (24 September 1903, in Preston, Lancashire – 10 November 1976, in Tring) was a British botanist, Keeper of Botany at the British Museum (Natural History) between 1956 and 1966. He was a world specialist on the plant genus Potamogeton and the family Magnoliaceae.
Dandy was educated at Preston Grammar School and after that at Downing College, Cambridge, where he took his B.A.. In 1925, he was appointed as an assistant to John Hutchinson at Kew Gardens, who worked on a new Angiosperm classification. He gave Dandy the opportunity to revise three taxa, one of which was Magnoliaceae. He became Fellow of the Linnean Society in 1927. On 11 July the same year, he was appointed Second class Assistant at the British Museum Department of Botany. He stayed here until his retirement in 1966. In 1936 he was promoted to First class Assistant, in 1946 to Principal Scientific Officer, and in 1956 he eventually became Keeper of Botany. After his retirement, he kept active in the field of botany until he fell seriously ill, in July 1976.