Matti Nykanen, a Finnish ski jumping champion who won four Olympics titles in the 1980s and later struggled with alcohol abuse and outbursts of violent behavior, died Feb. 3. He was 55.

The International Ski Federation (FIS) announced the death but did not say where he died. The cause was not immediately known, according to the federation.

Mr. Nykanen was a sports icon in Finland. Nicknamed the Flying Finn, he was 18 when he won his first competition in the storied Four Hills Tournament, yet with his boyish looks seemed even younger.

At the 1984 Olympics in Sarajevo, then part of Yugoslavia, he won a silver medal in the normal hill event and took the gold in the large hill, winning by 17.5 points — “the largest margin in Olympic history,” according to the International Olympic Committee. Four years later at the Winter Games in Calgary, Alberta, he took all three gold medals, winning the normal hill and large hill as well as the inaugural team competitions.

Mr. Nykanen also won seven World Championship gold medals.

“He is a legend of his sport,” Thomas Bach, president of the IOC, said in a statement. “Our thoughts are with his family and his friends.”

Mr. Nykanen retired in 1991 after winning a then-record 46 individual World Cup events.

“Nykanen has been one of our great ambassadors for the sport of skiing in general, with all the medals and cups he won,” FIS President Gian Franco Kasper said at the Alpine skiing world championships in Are, Sweden.

Mr. Nykanen’s success on skis was balanced by a troubled personal life. He was twice sentenced to prison for violent behavior: a stabbing incident in 2004 and an aggravated assault on his former wife in 2009. After retiring, he recorded a hit album and worked briefly as a stripper.

Several biographies have been written about Mr. Nykanen, and he was the subject of a 2006 movie, “Matti: Hell Is for Heroes,” that drew record audiences in Finland.

Matti Ensio Nykanen was born in Jyvaskyla, Finland, on July 17, 1963. A complete list of survivors was not immediately available.