M. Penn Phillips, born Marion Phillips, (13 June 1887, Parsons, Kansas – 24 May 1979, Sierra Madre, California) was an American entrepreneur and prominent real estate developer. He founded the M. Penn Phillips Company which, as a subsidiary of Holly Development Corporation, operated in the Western states from the 1920s through the 1970s. His development projects focused on building new communities, including Hesperia and Salton City in California and Christmas Valley in Oregon.
In 1923 he opened the new subdivision of Clear Lake Highlands near Clear Lake, California which, in 1980, became part of newly incorporated Clearlake.
In 1955, he was president of Hesperia Land Development and Hesperia Sales Corporation, while conceiving the U-Finish Home, mass-produced housing units which were completely finished on the outside leaving the buyer to complete the interior.
In 1956, he was an alternate delegate from California to the Republican National Convention.
Finally, Salton City, a community on the west shore of the Salton Sea was mapped out by the M. Penn Phillips Company in 1958.
He was a benefactor to Claremont McKenna College for whom Phillips Hall was named in 1966.