Victor French, an actor and director who played leading roles in the television series ''Highway to Heaven,'' ''Little House on the Prairie'' and ''Gunsmoke,'' died of lung cancer on Thursday at Sherman Oaks Community Hospital. He was 54 years old.

Mr. French was diagnosed with lung cancer three months ago, said his business manager, Bob Philpott, and was admitted to the hospital last week.

He was born in Santa Barbara to a Hollywood stunt man. The burly, bearded actor was known early in his career as a leading television villain. He appeared in ''Gunsmoke'' more than 20 times and directed five of the episodes. He was frequently seen in ''Bonanza.''

He subsequently played the scruffy farmer Isaiah Edwards on ''Little House on the Prairie,'' starring Michael Landon. Beneath his character's tough exterior was a kind, gentle man. In 'Carter Country'

Mr. French left the series in 1977 to star in his own situation comedy, ''Carter Country,'' playing a police chief in a city not far from Plains, Ga., home of former President Jimmy Carter. After ''Carter Country'' was canceled by ABC, he rejoined ''Little House'' in 1982, staying with it until the next year.

He teamed up with Mr. Landon again in NBC's ''Highway to Heaven'' in 1984, playing Mark Gordon, an embittered former policeman.

Mr. French directed every third episode of ''Highway to Heaven.'' He also played Agent 44 on ''Get Smart'' and appeared in the short-lived situation comedy ''The Hero'' on NBC in 1966. His films included the westerns ''Charro'' with Elvis Presley, and ''Flap'' with Anthony Quinn. On stage he won praise for his performance as a bar owner in a 1971 revival of William Saroyan's play ''The Time of Your Life,'' which stared Henry Fonda.

Mr. French also directed for the theater, winning a Los Angeles Drama Critics Award for his production of ''12 Angry Men.''

Mr. French is survived by three children, Tracy, Kelly and Victor Jr.

V E French