Roger Corman, who for decades dominated the world of B movies as the producer or director of countless proudly low-budget horror, science fiction and crime films, has died. He was 98.

He died on Thursday at his home in Santa Monica, Calif., his family said in a statement posted late Saturday on his official Instagram page. The statement did not specify the cause of death.

Mr. Corman produced more than 300 films and directed roughly 50 of them (the exact number is hard to determine, because he directed or helped direct some without a credit), including cult classics like “A Bucket of Blood” (1959), “The Masque of the Red Death” (1964), “The Wild Angels” (1966) and the original “The Little Shop of Horrors” (1960), which he shot for $35,000 in two days on a set left over from somebody else’s movie. When he got tired of directing, he opened the door to Hollywood for talented young protégés like Francis Ford Coppola (“Dementia 13”), Martin Scorsese (“Boxcar Bertha”), Jonathan Demme (“Caged Heat”), Peter Bogdanovich (“Targets”) and Ron Howard (“Grand Theft Auto”).

Mr. Corman “was able to nurture other talent in a way that was never envious or difficult, but always generous,” Mr. Scorsese said of him. “He once said: ‘Martin, what you have to get is a very good first reel, because people want to know what’s going on. Then you need a very good last reel, because people want to hear how it all turns out. Everything else doesn’t really matter.’ Probably the best sense I have ever heard about the movies.”

Among the others Mr. Corman nurtured was Jack Nicholson, who was 21 when Mr. Corman gave him his first movie role, the lead in “The Cry Baby Killer” (1958), and 23 when he had a small part as a masochistic dental patient in “The Little Shop of Horrors.” Before he went on to stardom, Mr. Nicholson acted in eight Corman movies and wrote three of them, including “The Trip,” an uncautionary tale about LSD.