Harley Harris Bartlett (born Anaconda, Montana, March 9, 1886 – February 21, 1960) was American botanist and biochemist. He was head of the Department of Botany at the University of Michigan from 1922 to 1947, and director of the university's Botanical Gardens, from 1919 to 1955.
He studied chemistry at Harvard University, receiving his AB in 1908. He was then hired by Bureau of Plant Industry of the United States Department of Agriculture, where he worked on plant nutrition and biochemistry as well as taxonomy, and began publishing on the genetics of the genus Oenothera (evening primroses), which he pursued into his years at Michigan and for which he became widely known. He joined the faculty of the University of Michigan in 1915, where he spent the majority of his career. He served as president of the Botanical Society of America (1927) and the Michigan Academy of Science, Arts, and Letters (1924–25). He is commemorated in the name of the genus Bartlettina.
The standard author abbreviation Bartlett is used to indicate this individual as the author when citing a botanical name.