John Richard Coulter (born 3 December 1930) is an Australian medical researcher and former politician. He was the fourth elected parliamentary Senate leader of the Australian Democrats, serving from 2 October 1991 to 29 April 1993. His understanding of conservation and environment principles was exceptional for the time, though his concern about Australian immigration and population growth occasionally brought him into conflict with the party's non-discriminatory humanitarian and human-rights platforms. He first took office in the Senate in 1987, representing South Australia, and resigned from the Senate on 20 November 1995 (excerpt from Wikipedia).

John has been active with Sustainable Population Australia (SPA) since the organisation's inception as Australians for an Ecologically Sustainable Population in 1988. He has supported the organisation in various roles, including President, Vice-President and Treasurer. He is currently active as the Representative for South Australia and Northern Territory on the SPA executive committee.

John Coulter has been a guest on 2 episodes.