Ackerman was the editor and principal writer of the American magazine Famous Monsters of Filmland, as well as an actor, from the 1950s into the 21st century. He appears in several documentaries related to this period in popular culture, like Famous Monster: Forrest J Ackerman (directed by Michael R. MacDonald and written by Ian Johnston), which premiered at the Egyptian Theatre in March 2009, during the Forrest J Ackerman tribute; The Ackermonster Chronicles! (a 2012 documentary about Ackerman by writer and filmmaker Jason V Brock); and Charles Beaumont: The Short Life of Twilight Zone's Magic Man, about the late author Charles Beaumont, a former client of The Ackerman Agency.
Also called "Forry", "Uncle Forry", "The Ackermonster", "Dr. Acula", "Forjak", "4e" and "4SJ", Ackerman was central to the formation, organization and spread of science fiction fandom and a key figure in the wider cultural perception of science fiction as a literary, art, and film genre. Famous for his word play and neologisms, he coined the genre nickname "sci-fi". In 1953, he was voted "#1 Fan Personality" by the members of the World Science Fiction Society, a unique Hugo Award never granted to anyone else.
He was also among the first and most outspoken advocates of Esperanto in the science fiction community.
Ackerman was born Forrest James Ackerman (though he would refer to himself from the early 1930s on as "Forrest J Ackerman" with no period after the middle initial), on November 24, 1916, in Los Angeles, to Carroll Cridland (née Wyman; 1883–1977) and William Schilling Ackerman (1892–1951). His father, Chief Statistician for the Associated Oil Company, and assistant to the Vice-President in charge of transportation, was from New York and his mother was from Ohio (the daughter of architect George Wyman); she was nine years older than William.