Elmer Drew Merrill (October 15, 1876 – February 25, 1956) was an American botanist, specializing in the flora of the Asia-Pacific region.
He was born in East Auburn, Maine, and attended the University of Maine where he received a B.S. in 1898. He subsequently joined the United States Department of Agriculture and served as a USDA botanist in the Philippines from 1902 to 1923.
He returned to the United States and became the Dean of the College of Agriculture, University of California, Berkeley. In 1929 he moved to New York to become a professor of botany at Columbia University. He was also the Director of the New York Botanical Garden from 1929 to 1935. In 1935 he became director of the Arnold Arboretum, Harvard University where he remained until his retirement in 1946.
He was known for his extensive study of the taxonomy of plants from Asia. His writings included Flora of Manila published 1912, and The Enumeration of Philippine Flowering Plants published in sections between 1922 and 1926. His final work The Botany of Cook's Voyages was published in 1954.
He died in Forest Hills, Massachusetts.