Robert Harding Whittaker (December 27, 1920 – October 20, 1980) was an American plant ecologist, active in the 1950s to the 1970s. He was the first to propose the five kingdom taxonomic classification of the world's biota into the Animalia, Plantae, Fungi, Protista, and Monera in 1969. He also proposed the Whittaker Biome Classification, which categorized biome-types upon two abiotic factors: temperature and precipitation.