James Hamlyn "Jim" Willis (28 January 1910 – 10 November 1995) was an Australian botanist. He described 64 new species of plants,and published more than 880 works including the landmark two volume A Handbook to plants in Victoria between 1962 and 1973.
Willis was born in Oakleigh, Victoria in 1910. In 1913 he moved with his family to Stanley on the northern coast of Tasmania, Australia where they remained until returning to Victoria in 1924. He attended Melbourne High School and in 1928, following receipt of a scholarship, began studies at the Victorian School of Forestry in Creswick, graduating with a Diploma of Forestry in 1930. For the next seven years he was employed by the Victoria Forests Commission as a forest officer.
In 1937 Willis joined the National Herbarium, Melbourne and commenced studies at the University of Melbourne, graduating with a Bachelor of Science (Honours) in 1940. Between 1958 and 1959, he held the position of Australian Botanical Liaison Officer at the Royal Botanic Gardens, Kew, and in 1961 he was appointed as Assistant Government Botanist for Victoria. Between 1970 and 1972, he was the Acting Director of the Royal Botanic Gardens, Melbourne.