Charles S. "Sasha" Zimmerman (1896–1983) was an American socialist activist and trade union leader, who was an associate of Jay Lovestone. Zimmerman had a career spanning five decades as an official of the International Ladies Garment Workers Union. During the early 1970s, Zimmerman and Bayard Rustin were national Co-Chairmen the Socialist Party of America and the Social Democrats USA.

Social Democrats, USA (SDUSA) is a social-democratic organization established in 1972 as the successor of the Socialist Party of America (SPA). The SPA had stopped running independent presidential candidates and consequently the term "party" in its name had confused the public. Moreover, replacing the "socialist" label with "social democrats" was meant to disassociate the group from the Soviet Union.