John Hamilton Tanton (1934–2019) was an American ophthalmologist, eye surgeon, biologist, and environmentalist who became a pivotal architect and key figure in the contemporary U.S. immigration restriction movement, often described as a white nationalist. Born on February 23, 1934, in Detroit, Michigan, to John Fitzgerald Tanton, a Canadian immigrant, and Hannah Koch Tanton, he spent his early childhood in Detroit before the family relocated to his mother's family farm in eastern Michigan in 1945. Tanton pursued higher education at Michigan State University, earning a bachelor's degree in chemistry in 1956, followed by an M.D. from the University of Michigan in 1960 and an M.S. in ophthalmology in 1964. He established a successful ophthalmology practice in Petoskey, Michigan, where he worked as an eye surgeon while developing interests in biology, environmentalism, and population control.

In the 1970s and 1980s, Tanton shifted focus to activism, founding the Federation for American Immigration Reform (FAIR) in 1979 as its first chairman to advocate for reduced immigration levels and population stabilization. He co-founded the Center for Immigration Studies (CIS) in 1985, a think tank promoting anti-immigration policies, and NumbersUSA in 1996, a lobbying group influencing immigration legislation. His efforts extended to environmental organizations like the Zero Population Growth committee, where he served as president from 1969 to 1975, linking overpopulation to ecological concerns. Tanton's network-building included funding and advising numerous restrictionist groups, amassing significant influence in conservative circles, though he was succeeded at FAIR by Dan Stein.

Tanton's activism drew widespread controversy for its alleged ties to white nationalism, eugenics, and racial anxieties about immigration's impact on American culture and demographics. The Southern Poverty Law Center labeled him a key figure in the white nationalist movement, citing his correspondence expressing concerns over 'Hispanics' lower intelligence' and support for eugenics. He faced criticism for founding U.S. English and U.S. Inc., organizations accused of promoting English-only policies to marginalize non-English speakers. Investigations and reports, including leaked memos from the 1980s, revealed his worries about the 'changing ethnic composition' of the U.S. Tanton denied racism but defended his views as cultural preservation. He died on July 16, 2019, in Petoskey, Michigan, at age 85, leaving a legacy of organizations that continue to shape immigration debates.