On the July 31 episode of "Raw", Lesnar was scheduled to defend his title in a fatal four-way match at SummerSlam against Samoa Joe, Roman Reigns and Braun Strowman. Lesnar and Heyman stated that both would leave WWE should Lesnar lose the championship in the match. At SummerSlam, Lesnar retained the title by pinning Reigns. The next night on "Raw", Lesnar was attacked by Strowman. The subsequent title match at No Mercy was won by Lesnar. Lesnar then defeated WWE Champion AJ Styles in an interbrand Champion vs Champion non-title match at Survivor Series. His next title defense was scheduled for the Royal Rumble where he successfully defended the title in a triple threat match against Strowman and Kane. Lesnar then re-ignited his feud with Roman Reigns, who won the Elimination Chamber match at Elimination Chamber to become the number one contender to Lesnar's title at WrestleMania 34. At WrestleMania, Lesnar pinned Reigns to retain the title in the main event. Afterwards, rumors arose that Lesnar would leave WWE and rejoin the UFC. However, on April 9, Lesnar re-signed with the WWE. At the Greatest Royal Rumble pay-per-view, he again defeated Reigns in a steel cage when Reigns speared Lesnar through the cage wall. As Lesnar escaped the cage first, he was declared the winner.