Emlyn Williams, 81, the Welsh actor and playwright who wrote "The Corn Is Green" and did notable one-man shows of the works of Charles Dickens and Dylan Thomas, died today at his home in London. He had cancer.

The son of a factory worker, Mr. Williams spoke only Welsh until he went to school. He won scholarships to study in France and at Oxford University, where he joined the drama society and fell in love with the stage.

His pride in his Welsh background brought him into contact with such eminent compatriots as Thomas and actor Richard Burton.

His first play, "A Murder Has Been Arranged," was staged in 1930. Five years later, his macabre thriller "Night Must Fall" became a hit, with Mr. Williams playing the leading role in London and New York.

In 1938, he appeared as Morgan Evans, a young Welsh coal miner, opposite Sybil Thorndike in "The Corn Is Green," a smashing success that won the New York Drama Critics' Circle Award for best foreign play of the year. It was recently revived in London starring Deborah Kerr and in New York starring Cicely Tyson.

Mr. Williams first appeared in films in 1932, and in 1948 he wrote, directed and starred in "The Last Days of Dolwyn," a drama about a Welsh village threatened by a dam construction project. Richard Burton made his film debut in the movie.

Mr. Williams played Sir Thomas More after Paul Scofield in the New York run of Robert Bolt's "A Man for All Seasons," and had a memorable cameo part as the eccentric, kite-flying Mr. Dick in the 1969 film version of "David Copperfield."

His one-man show based on works of Dickens toured the world and won rave reviews in Britain and the United States.

Mr. Williams spent his last years in semiretirement, emerging only occasionally into the public eye with a novel, "Headlong," published in 1980, a part in the 1983 television series, "Rumpole of the Bailey," and a part in the 1986 television movie, "Past Caring," a love triangle set in a home for the elderly.

A newspaper once accidentally published Mr. Williams' obituary, an oversight that apparently amused him immensely. "They say I died in 1974," he told an interviewer, "but I have wracked my brains and cannot recall anything untoward happening that year."

His wife, Irish actress Molly O'Shann, whom he married in 1935, died in 1970.

Survivors include two sons, Alan Emlyn Williams, a mystery writer, and Brook Richard Williams.