Richard Eric Holttum (20 July 1895 – 18 September 1990) was an English botanist and author.
Holttum was born 20 July 1895 in Cambridgeshire, England, to English store owners of Quaker faith. He was educated at Bootham School, York. He studied at the University of Cambridge.
Having received botanical training, Holttum was given the role of assistant director at the Singapore Botanical Gardens in 1922, with the guidance of Isaac Henry Burkill. In Singapore, he performed some exhaustive studies, and was promoted to director in 1925, following the retirement of Burkill. His areas of expertise were the growth and cultivation of orchids. He continued working at the Singapore Botanical Gardens even during the Japanese occupation of the country. Returning from Great Britain, where he departed to in 1925, Holttum continued his job as the Garden's director, until he moved to the University of Malaya in Singapore to serve as its first Professor of Botany. Holttum penned many books during his tenure at the educational institution, including Gardening at the lowlands of the Malays (which is credited as the first book on Singaporean gardening) and Plant Life in Malaya. He was also the first head of department for Botany at the Department of Biological Sciences at the National University of Singapore. He founded the Malayan Orchid Society (now Orchid Society of South East Asia) in 1928. He went back to England later in 1954.
Holttum's area of interest was pteridology, such as that of Malayan ferns.
Spending some time at the Kew Gardens to work, Holttum died 18 September 1990 in Roehampton, London, aged 95.