The 25-year-old software engineer from Los Angeles, whose name was not released at his request, won after putting three $1 coins in a machine at the Excalibur hotel-casino, said Rick Sorensen, a spokesman for slot machine maker International Game Technology.
The progressive Megabucks Jackpot is generally paid out in equal amounts over 25 years, although winners can negotiate other payoffs, Sorensen said.
The system links dollar slot machines in 157 Nevada casinos.
The previous record was about $34.9 million, won at the now-closed Desert Inn in Las Vegas on Jan. 26, 2000.
The jackpot had been building since May 27, 2002, when a woman at Bally's hotel-casino in Las Vegas won $22.6 million.