Noun
founding member (plural founding members)
(US) A member of an organization that was involved in, or whose membership commenced with, the organization's foundation.
The United Nations had 77 founding members.
Synonyms: charter member, (UK) founder member
As a right-wing conservative and founding member of the Freedom Caucus, I never expected that the co-worker I would work closest, and best, with at the White House would be a "globalist." Mick Mulvaney
My mother was a great advocate of women's rights, a member of the League of Women's Voters and lifelong member of Planned Parenthood and an advocate of a woman's rights in terms of reproductive issues. She was also a founding member of Common Cause in the state of Indiana. Kathryn Lasky
I was a founding member of the 'Dungeons and Dragons' club at my high school. I was in chorus, I was in swing choir. I was an outcast but I was an outcast among a group of outcasts. John C. Reilly
Ho, or Nguyen Ai Quoc, thus became the first Vietnamese communist and a founding member of the French Communist party, born out of the split. Wilfred Burchett