The biggest slot jackpot ever won was a staggering $39.7 million. This life-changing win occurred in March 2003 at the Excalibur Casino in Las Vegas. The lucky winner was a 25-year-old software engineer from Los Angeles. This record-breaking jackpot was won on a Megabucks slot machine. The massive payout instantly made headlines worldwide. The allure of hitting the biggest slot jackpot continues to captivate casino goers globally.