In June 2002 , Lesnar won the King of the Ring tournament , defeating Bubba Ray Dudley in the first round , Booker T in the quarter @-@ finals , Test in the semi @-@ finals , and Rob Van Dam in the finals , earning him a shot at the WWE Undisputed Championship at SummerSlam . On July 22 , Lesnar joined the SmackDown ! brand . After a quick feud with Hollywood Hulk Hogan in August 2002 , Lesnar defeated WWE Undisputed Champion , The Rock at SummerSlam to become the WWE Undisputed Champion and youngest WWE Champion at age 25 , a record previously held by The Rock . He also became the second fastest wrestler to win the WWE Championship since his debut ( 126 days ) behind only Ric Flair ( 113 days ) . At the time , the Undisputed WWE Championship was being defended on both brands , so Raw General Manager Eric Bischoff expected Lesnar to return to Raw the following night . However , SmackDown ! General Manager Stephanie McMahon announced that Lesnar was only required to defend the title on SmackDown ! , forcing Bischoff to institute a new championship for Raw ( the World Heavyweight Championship ) . The WWE Undisputed Championship was then renamed the WWE Championship .