Brock Lesnar (Universal Champion) – 504 days
The number one spot in the list of longest-reigning champions belongs to none other than the most dominant athlete in the history of combat sports. Brock Lesnar captured the Universal Championship by conquering Goldberg at WrestleMania 37. He then went on to defeat the likes of Braun Strowman, Kane, Finn Balor, Roman Reigns, Samoa Joe to continue that reign until SummerSlam 2018 where Roman Reigns finally brought the gold back on Raw. But Lesnar solidified himself his legacy to be the biggest box office attraction in WWE with this reign.