Seymour Posner (1925-1988), New York State assemblyman and labor legislator, was born on May 21, 1925 to Nathan and Fannie Posner. He was raised in the Bronx, New York. In 1942, he enlisted and served in the 3rd Infantry Regiment in France and Germany during World War II, during which he lost hearing in one ear. Upon his return to New York, Posner enrolled at the City University of New York, earning a BS in social science in 1948. He began his active involvement in Democratic politics during this time, as a supporter and officer in the Young Democrats. His involvement with the labor movement also began about this time, as he chaired the organizing committee of Local 371 of the Government and Civic Workers (AFSCME) from 1949 to 1951 and was a member of the New York City Central Labor Council from 1949 to 1954. In 1958 Posner completed the MA program at New York University's School of Public Administration.

Posner became the public relations director for the Urban League of Greater New York in 1958 and served as director of public relations for marches on Washington in 1958 and 1959, and again for the 1963 march led by Dr. Martin Luther King, Jr. He also spent several days in a Maryland jail as a Freedom Rider in 1963. Posner served as the community relations director to the Manhattan Borough President for one year (1961-1962) and was Bronx director of the American Jewish Congress (ca. 1962-1964). During this period he worked in public relations and direct-mail marketing of services primarily aimed at the housing market. In 1964 Posner sought and won the 76th A.D. Assembly spot, representing the South Bronx. Despite two consecutive reapportionments of the 76th district in 1965 and 1966, Posner was able to win re-election and became a fixture in the Assembly. He communicated with his constituency via newsletters and flyers. He concentrated on labor-related issues, supporting bills that permitted collective bargaining rights for domestic workers and for workers employed by non-profit, educational and charitable institutions and that guaranteed workman's compensation for farm workers. He sponsored bills on retirement benefits, insurance, and workman's compensation.

In 1972 he began serving on the Assembly Labor Committee, rising to the position of Chairman (1974-1976). He failed in a 1973 bid for the position of Bronx City Councilman at Large, and, in 1978, retired from the Assembly to accept appointment an from Governor Carey to the State Workman's Compensation Board, though his nomination was only narrowly confirmed by the Senate. Posner had some difficulties with two chairmen of the Board, Robert Steingut and Arthur Cooperman, but he did win appointment as the Vice-Chairman of the Board in 1984. Posner took a decidedly pro-union position on the Board and served until June of 1988, when he retired. He acted as the legislative director for the New York City Central Labor Council until his death on November 2, 1988, a span of less than six months.