TOKYO (AP) _ A new film festival that promoters hope will become one of the film world's great events opened today with the premiere of ''Ran,'' a Shakespearean story in a Japanese feudal setting by Japan's most acclaimed director, Akira Kurosawa.

A total of 137 films from 42 countries are to be screened during the 10-day festival.

Masato Hara, executive director of the festival, said he would like to make it an annual event and that he wants it to be one of the major world film festivals.

The competition section of the first Tokyo International Film Festival, called Young Cinema '85, offers the winner a prize of $1.5 million toward production of his next film. It is open to directors born after 1945 and who have released fewer than five commerical films.

Young directors entered 519 films in the contest, and a special screening committee has narrowed the field to 16 films.

A ''most promising filmmaker'' will be selected, based on combined evaluation of a completed film and future film plans, organizers said.

Large crowds were expected for showings of David Lean's ''A Passage to India,'' Y. Chahine's ''Adieu Bonaparte,'' John Korty's ''Ewok'' and such award-winners as ''Naplo,'' a Hungarian film selected for the special jury grand prize at Cannes in 1984 and the ''Killing Fields.''

However, for many the main attraction was the premiere of ''Ran'' or Turmoil, which was not completed in time for the last Cannes Film Festival.

Director Kurosawa spent nine months shooting his 27th film, which he has said ''is to round out my life's work in films.'' It cost $10.4 million, unusually expensive for a Japanese film.

The 75-year-old director has described ''Ran'' as a rendition of Shakespeare's King Lear in a Japanese setting from the 16th-century feudal period.

554EDT