Strikeforce was an American mixed martial arts and kickboxing organization based in San Jose, California that operated from 1985 to 2013.

In early 2011, Strikeforce was purchased by American Ultimate Fighting Championship owner Zuffa LLC, which eventually closed the promotion and brought the remaining fighter contracts into the UFC roster.

Its first MMA event, Strikeforce: Shamrock vs. Gracie, was held on March 10, 2006, at the HP Pavilion in San Jose, California.

They still ran multiple shows a year from HP Pavilion, as the owners of that building's main tenant, hockey's San Jose Sharks, had purchased a significant share in the promotion.

[5] During August 2009, Strikeforce CEO Scott Coker announced that it had signed formal alliances with Japanese MMA-promotion Dream and Russian promotion M-1 Global.

[6] As a result, Dream fighters such as Shinya Aoki, Tatsuya Kawajiri, Sergei Kharitonov, Melvin Manhoef, Jason Miller, Gegard Mousasi, Ronaldo Souza, Hiroyuki Takaya, and Marius Zaromskis competed in Strikeforce between 2009 & the partnership's end in 2011.

[7] On August 3, 2009, former Pride and reigning WAMMA Heavyweight Champion Fedor Emelianenko signed a 3-fight contract with Strikeforce, with events he competed on co-promoted by his promotional team M-1 Global.

Emelianenko next fought as part of the Strikeforce Heavyweight World Grand Prix Tournament,[10] losing again to Antônio Silva via doctor stoppage.

[12] On March 12, 2011, Dana White revealed on AOL to Ariel Helwani that Zuffa, LLC, the parent company of the UFC, had purchased Strikeforce.

Strikeforce CEO Scott Coker announced the return of Fedor Emelianenko on an unspecified July or August event and said that the Zuffa-owned company would continue to co-promote with M-1 Global.

[14] Following the purchase, the UFC signed many of Strikeforce's top stars and champions, such as Jason Miller, Nick Diaz, Dan Henderson, Alistair Overeem, Luke Rockhold, and Cung Le.

Notable fighters included Nick Diaz, Daniel Cormier, Josh Barnett, Ronda Rousey and Luke Rockhold.

Following a brief period away from fight promotion, former Strikeforce CEO Scott Coker would then go on to join Bellator MMA in June 2014, replacing Bjorn Rebney as its new president.