A number of notable people have considered themselves Unitarians, Universalists, and following the merger of these denominations in the United States and Canada in 1961, Unitarian Universalists. Additionally, there are persons who, because of their writings or reputation, are considered to have held Unitarian or Universalist beliefs. Individuals who held unitarian (nontrinitarian) beliefs but were not affiliated with Unitarian organizations are often referred to as "small 'u unitarians. The same principle can be applied to those who believed in universal salvation but were not members of Universalist organizations. This article, therefore, makes the distinction between capitalized "Unitarians" and "Universalists" and lowercase "unitarians" and "universalists".

The Unitarians and Universalists are groups that existed long before the creation of Unitarian Universalism.

Early Unitarians did not hold Universalist beliefs, and early Universalists did not hold Unitarian beliefs. But beginning in the nineteenth century the theologies of the two groups started becoming more similar.

Additionally, their eventual merger as the Unitarian Universalist Association (UUA) did not eliminate divergent Unitarian and Universalist congregations, especially outside the US. Even within the US, some congregations still keep only one of the two names, "Unitarian" or "Universalist". However, with only a few exceptions, all belong to the UUA—even those that maintain dual affiliation (e.g., Unitarian and Quaker). Transcendentalism was a movement that diverged from contemporary American Unitarianism but has been embraced by later Unitarians and Unitarian Universalists.

In Northern Ireland, Unitarian churches are officially called "Non-Subscribing Presbyterian", but are informally known as "Unitarian" and are affiliated with the Unitarian churches of the rest of the world.

A Francis Ellingwood Abbot (1836–1903) – Unitarian minister who led a group that attempted to liberalize the Unitarian constitution and preamble. He later helped found the Free Religious Association.Biographical Information for Abbot, Francis Ellingwood. Family Papers, 1815–1940, in the collections of the Andover-Harvard Theological Library, Harvard Divinity School. Retrieved August 28, 2007. Abigail Adams (1744–1818) – women's rights advocate and first Second Lady and the second First Lady of the United StatesAbigail Adams James Luther Adams (1901–1994) – Unitarian theologian.Notable American Unitarians, 1936–1961, a project of the First Parish and the First Church in Cambridge (Unitarian Universalist), hosted at the website of Harvard Square Library. Project advisors: Gloria Korsman, Andover-Harvard Theological Library; Conrad Edick Wright, Massachusetts Historical Society; and Conrad Wright, Harvard Divinity School. (Archived July 3, 2007) John Adams (1735–1826)"Some famous Unitarians include presidents John Adams and John Quincy Adams, Louisa May Alcott, Ralph Waldo Emerson, Paul Revere, President William Howard Taft, and Frank Lloyd Wright... Important figures from this period in Unitarian history include John Biddle, Francis David, Michael Servetus, King John Sigismund and Faustus Socinus... The influential Unitarians from this era included William Ellery Channing, Theodore Parker, Joseph Priestly [sic], and Thomas Starr King, who was also a Universalist." , uduuf.org. Retrieved August 1, 2011. – second president of the United States. John Quincy Adams (1767–1848) – sixth president of the United States and co-founder of Unitarian All Souls Church, Washington, D.C. Sarah Fuller Adams (1805–1848) – English poet and hymn writer Conrad Aiken (1889–1973) – poet Louisa May Alcott (1832–1888) – author of Little Women. Horatio Alger Sr. (1806–1881) – Unitarian Minister father of Horatio Alger. Ethan Allen (1738–1789) – author of Reason the Only Oracle of Man, and the chief source of Hosea Ballou's universalist ideasRecent Scholarship in American Universalism: A Bibliographical Essay, Alan Seaburg, Church History, Vol. 41, No. 4. (Dec., 1972), pp. 513–523. Retrieved August 28, 2007. Joseph Henry Allen (1820–1898) – American Unitarian scholar and minister Arthur J. Altmeyer (1891–1972) – father of Social Security Oliver Ames Jr. (1807–1877) – Massachusetts businessman and industrialist who commissioned the building of the Unity Church of North Easton J. M. Andrews (1871–1956) – Prime Minister of Northern Ireland (a Non-subscribing Presbyterian member) L.F.W. Andrews (1802-1875) - American Southern Universalist minister and a prodigious publisher of denominational and secular newspapers. Thomas Andrews (1873–1912) – Master-shipbuilder of the RMS Oceanic (1899), "Big Four", and Olympic-class ocean liners (a Non-subscribing Presbyterian member) Tom Andrews (born 1953) – Former U.S. Representative from Maine, current United Nations Special Rapporteur on Human Rights in Myanmar Susan B. Anthony (1820–1906) – Quaker"Delineated in detail are formative influences such as her... religious environment (Quaker and Unitarian)..." Suffrage for All, Review of Susan B. Anthony: Rebel, Crusader, Humanitarian by Alma Lutz. Review author: Hazel Browne Williams, The Phylon Quarterly, Vol. 20, No. 2. (2nd Qtr., 1959), p. 205. Retrieved August 25, 2007. Robert Aspland (1782–1845) – English Unitarian minister, editor and activist, founder of the British and Foreign Unitarian Association Robert Brook Aspland (1805–1869) – English Unitarian minister and editor, son of Robert Aspland

B Samuel Bache (1804–1876) – English Unitarian minister E. Burdette Backus (1888–1955) – Unitarian Humanist minister (originally a Universalist) Blanche Pentecost Bagley (1858–1928) – British-born American Unitarian minister Bill Baird (born 1932) – abortion rights pioneer, Unitarian. Sara Josephine Baker (1873–1945) – physician and public health worker. Emily Greene Balch (1867–1961) – Nobel Peace Laureate Roger Nash Baldwin (1884–1981) – founder of American Civil Liberties Union Adin Ballou (1803–1890) – abolitionist and former Baptist who became a Universalist minister, then a Unitarian minister. Hosea Ballou (1771–1852) – American Universalist leader. (Universalist minister and a unitarian in theology)"Ballou, the son of a poor Calvinist Baptist preacher, was converted to Universalism and began preaching the new "heresy" on a Calvinistic basis in 1791… His first sermon on a Unitarian and Arian base was preached in 1795. Within ten years, through the power of his argumentation, and against the opposition of the prominent Universalist John Murray, Ballou had converted the Universalist ministry to Unitarianism."Hosea Ballou, Preacher of Universal Salvation, Ernest Cassara, Church History, Vol. 26, No. 4. (Dec., 1957), p. 382. Retrieved August 25, 2007."Some famous Universalists include Clara Barton, Olympia Brown, Thomas Starr King, Horace Greeley, George Pullman, Mary Livermore, and Benjamin Rush. ...Universalist beliefs have been proclaimed for thousands of years, starting with Origen in 200 CE and continuing through to James Relly in the sixteen hundreds... Universalists including Hosea Ballou, John Murray, and Benjamin Rush helped to spread and develop their faith's teachings throughout the denomination's early years." Universalism, UUA.org, August 1, 2007. Retrieved August 27, 2007. Aaron Bancroft (1755–1839) – Congregationalist Unitarian minister John Bardeen (1908–1991) – physicist, Nobel Laureate 1956 (inventing the transistor) and in 1972 (superconductivity) Phineas Taylor Barnum (1810–1891) – American showman and Circus OwnerSeaburg, Alan. P. T. Barnum . Unitarian Universalist Historical Society. Retrieved February 20, 2008. Ysaye Maria Barnwell (born 1946) – member of Sweet Honey in the Rock, founded the Jubilee Singers, a choir at All Souls Church in Washington, D.C. Béla Bartók (1881–1945) – composer. Clara Barton (1821–1912) – organizer of American Red Cross, Universalist"The Struggle for Racial Justice describes the key roles played by Unitarian and Universalist women... These women included Clara Barton, founder of the American Red Cross, and Julia Ward Howe, who wrote 'The Battle Hymn of the Republic.'" Exhibit "Standing Before Us: Unitarian Universalist Women and Social Reform" On Display at Women's Rights National Historical Park, Women's Rights National Historical Park news release, Department of the Interior, National Park Service, Contact: Vivien Rose. Retrieved August 28, 2007. Clara Bancroft Beatley (1858–1923) – educator, lecturer, author Christopher C. Bell (born 1933) – author Ami Bera (born 1965) – U.S. Representative for California Henry Bergh (1811–1888) – founded the American Society for the Prevention of Cruelty to Animals and the Society for the Prevention of Cruelty to Children."Bergh used his wealth and prestige to raise public awareness of the suffering of animals and to enlist support from powerful New York businessmen, politicians, and religious leaders in the founding of the ASPCA. Among these was his minister, Henry Whitney Bellows of the First Congregational Church of New York City (now the Unitarian Church of All Souls)" http://www25-temp.uua.org/uuhs/duub/articles/henrybergh.html Tim Berners-Lee (born 1955) – inventor of the World Wide Web."Some Unitarian Universalists of whom you may already have heard include Tim Berners-Lee, Paul Newman, Christopher Reeve, May Sarton, Pete Seeger, and Kurt Vonnegut... Unitarian Universalists James Reeb and Viola Liuzzo were killed because of their participation in this protest..." Unitarian Universalism, UUA.org, March 1, 2007. Retrieved August 28, 2007. Tim Berners-Lee, The World Wide Web and the "Web of Life" Paul Blanshard (1892–1980) – activist. Joani Blank (1937–2016) – sexuality educator and co-housing activist.Joani Blank, Cohousing: What's so UU about it? Chester Bliss Bowles (1901–1986) – Connecticut Governor and diplomat. Ray Bradbury (1920–2012) – author. Andre Braugher (1962–2023) – American actor T. Berry Brazelton (1918–2018) – pediatrician, author, TV show host. Alice Williams Brotherton (1848–1930), poet and magazine writer Olympia Brown (1835–1926) – suffragist, Universalist minister of the Unitarian Universalist Church of Kent Ohio Percival Brundage (1892–1979) – technocrat"...he was director of the American Unitarian Association (1942–48) and in 1949 began the first of five years as a director of the Unitarian Service Committee (1949–54). Chairman, Unitarian Development Fund Campaign (1959–62)." Hall of Fame: Percival Flack Brundage, Fisher College of Business at The Ohio State University, 1994–2004. (Archived.) Retrieved August 26, 2007. John A. Buehrens (born 1947) – president of the Unitarian Universalist Association from 1993–2001 Charles Bulfinch (1763–1844) – most notable for being Architect of the Capitol. Co-founder, All Souls Church, Unitarian (Washington, D.C.) Ralph Wendell Burhoe (1911–1997) – scholar Harold Hitz Burton (1888–1964) – U.S. Supreme Court Justice 1945–1958 Edmund Butcher (1757–1822) – English minister

C John C. Calhoun (1782–1850) – U.S. Vice President and SenatorVision & Values in a Post-9/11 World: A curriculum on Civil Liberties, Patriotism, and the U.S. Role Abroad for Unitarian Universalist Congregations, Developed by Pamela Sparr on behalf of the Unitarian Universalist Association of Congregations, Spring 2002. Retrieved August 28, 2007. Co-founder, All Souls Church, Unitarian (Washington, D.C.) Walter Bradford Cannon (1871–1945) – experimental physiologist