Gary Gygax, a pioneer of the imagination who transported a fantasy realm of wizards, goblins and elves onto millions of kitchen tables around the world through the game he helped create, Dungeons & Dragons, died Tuesday at his home in Lake Geneva, Wis. He was 69.

His death was confirmed by his wife, Gail Gygax, who said he had been ailing and had recently suffered an abdominal aneurysm, The Associated Press reported.

As co-creator of Dungeons & Dragons, the seminal role-playing game introduced in 1974, Mr. Gygax wielded a cultural influence far broader than his relatively narrow fame among hard-core game enthusiasts.

Before Dungeons & Dragons, a fantasy world was something to be merely read about in the works of authors like J. R. R. Tolkien and Robert Howard. But with Dungeons & Dragons, Mr. Gygax and his collaborator, Dave Arneson, created the first fantasy universe that could actually be inhabited. In that sense, Dungeons & Dragons formed a bridge between the noninteractive world of books and films and the exploding interactive video game industry. It also became a commercial phenomenon, selling an estimated $1 billion in books and equipment. More than 20 million people are estimated to have played the game...