Alistair "Demolition Man" Overeem (born May 17 , 1980) is a professional Dutch mixed martial artist and current Strikeforce heavyweight champion.

After posting a 10-3 record in promotions such as RINGS, Overeem debuted in PRIDE on July 20, 2002, defeating Yusuke Imamura by TKO in just 45 seconds. Overeem would win two more fights in PRIDE before entering the 2003 PRIDE Middleweight Grand Prix at PRIDE Total Elimination 2003 before losing to future UFC light heavyweight champion Chuck Liddell in the quarterfinal match. Overeem rebounded to defeat Tomohiko Hashimoto at the Inoki Bom-Ba-Ye 2003-Inoki Festival in 36 seconds. On October 31, 2004 he fought Hiromitsu Kanehara, defeating him by TKO part-way through the first round at PRIDE 28 - High Octane. He lost his next fight against Brazilian Top Team fighter Antonio Rogerio Nogueira.

In 2005, Overeem entered the PRIDE Middle Weight Grand Prix at PRIDE Total Elimination 2005 where he defeated former UFC light heavyweight champion Vitor Belfort by submission in the opening round. Overeem would move on to fight Igor Vovchanchyn in the quarterfinals at PRIDE Critical Countdown 2005 taking under two minutes to win by submission. Overeem lost in the semi-finals to eventual champion Mauricio Rua.

In February 2006, Overeem fought Russian Top Team favorite Sergei Kharitonov. Overeem won the fight, dislocating Kharitonov's shoulder in the process. With his win over Kharitonov, Overeem secured a spot in the PRIDE 2006 Open Weight Grand Prix at PRIDE Total Elimination Absolute. He fought Brazilian Jiu-Jitsu specialist Fabricio Werdum, losing via kimura in the second round.

After his loss, Overeem traveled to San Jose, California to rematch Vitor Belfort at Strikeforce: Revenge. Despite being the main event, Overeem pulled out a decision win in a lackluster fight. A month later Overeem returned to PRIDE for a highly anticipated rematch with Antonio Rogerio Nogueira. Early in the second round, as Overeem stumbled from a punch, Nogueira threw a flurry of punches. Worried Overeem would be more severely injured, his corner threw in the towel.

At PRIDE Final Conflict Absolute, he lost to Ricardo Arona. Overeem was on the receiving end of a leg kick that caused a non-serious injury to his nerves, causing him to lose feeling in his foot and leg. Unable to mount an offense or defend against Arona, Overeem tapped out to avoid further injury.

He then suffered another KO loss to Mauricio Rua at Pride 33, but returned in June 2007 with a submission win over Michael Knaap at K-1 Grand Prix in Amsterdam (despite K-1 being a kickboxing promotion, the bout was fought under MMA rules).

On September 17, 2007, at K-1 Hero's Middleweight GP Final Alistair again faced Sergey Kharitonov. Overeem showed dominant movement as soon as the first round began,but he suffered a KO loss just before the end of the first round.

On November 16, 2007, Overeem defeated Paul Buentello for the vacant Strikeforce heavyweight title by submission due to knee strikes.

On June 15, 2008 Overeem won by KO in the first round against Lee Tae-Hyun at DREAM.4

Not too long ago, Overeem defeated K-1 World Grand Prix 2001 champion Mark Hunt in the first round by submission at DREAM.5.

His next fight was against Mirko Filipovic at DREAM.6 on September 23, 2008. After almost half of the first round which saw Overeem taking down Filipovic multiple times and effectively striking from the top position, cutting his Croatian foe, the bout was stopped and declared a no contest due to Alistair landing multiple knees to the groin of Filipovic.

Most recently Overeem faced Badr Hari, one of K-1's top contenders, under K-1 rules. He defeated Hari by way of knockout in the first round, achieving one of his most outstanding accomplishments to date.

In a recent 2008 interview, Overeem has stated that he would like to fight in the UFC in the near future. Overeem would ideally like a rematch in 2009 with Chuck Liddell to avenge his PRIDE Total Elimination 2003 knockout loss against him. Overeem was also seen at UFC 93 in Ireland talking to Dana White and indicating he is "ready" to fight in the UFC.