As of today (April 30, 2018), WWE Universal Champion Brock Lesnar is only 41 days short of equaling, and possibly surpassing, C.M. Punk's historic WWE Championship reign of 434 days. C.M. Punk is currently recognized as "the longest-reigning WWE World Champion of the 'modern era'" thanks to his November 20, 2011 - January 27, 2013 title reign.
Brock Lesnar’s Universal Championship reign is currently the 8th longest World Title Run in WWE history. Lesnar trails CM Punk by 41 days. The other 6 runs ahead of him are: Hulk Hogan, Bob Backlund (twice), Bruno Sammartino (twice) and Pedro Morales. pic.twitter.com/pi1OTR124W— WrestleVotes (@WrestleVotes) April 30, 2018