After leaving WWE in 2004, Lesnar pursued a career in the NFL. He played during the preseason for the Minnesota Vikings, but ended up being a late cut. Lesnar returned to professional wrestling at the end of 2005, and joined New Japan Pro Wrestling, where he won the IWGP Heavyweight Championship in his first wrestling match since leaving the WWE.He was stripped of the title in July 2006, although he held the physical belt until June 2007.
Lesnar started a career in mixed martial arts and had his first fight in June 2007. He then signed with the Ultimate Fighting Championship (UFC) in October 2007. Upon signing with the organization he had an unsuccessful debut against Frank Mir, but has since remained undefeated, capturing the UFC Heavyweight Championship from Randy Couture on November 15, 2008 and avenging his earlier loss to Mir by way of a second round TKO at UFC 100.