Strikeforce: Barnett vs. Cormier was a mixed martial arts event held by Strikeforce. It took place on May 19, 2012 at the HP Pavilion in San Jose, California.
Nate Marquardt was expected to fight Tyron Woodley at this event for the vacant Strikeforce Welterweight Championship.  It instead took place at Strikeforce: Rockhold vs. Kennedy, where Marquardt won the title by fourth round knockout.
Preliminary card (Showtime Extreme)
- Inocente defeated Zwicker via unanimous decision (29–28, 29–28, 30–27).
- Villante defeated Mehmen via unanimous decision (29–28, 30–27, 30–27).
- Mulhern defeated Villefort via split decision (30–27, 28–29, 29–28).
- Green defeated Terry via split decision (28–29, 29–28, 29–28).
- Vallie-Flagg defeated Cavalcante via split decision (29–28, 29–28, 28–29).
Main card (Showtime)
- Spång defeated Burrell via TKO (knees) at 3:25 of round 1.
- Cavalcante defeated Kyle via submission (guillotine choke) at 0:33 of round 1. Cavalcante subsequently tested positive for stanozolol in a post-fight drug test and the NSAC ruled the bout a NC.
- Melendez defeated Thomson via split decision (47–48, 48–47, 48–47) to retain the Strikeforce Lightweight Championship.
- Cormier defeated Barnett via unanimous decision (49–46, 50–45, 50–45) to become the Strikeforce Heavyweight Grand Prix Champion.
Heavyweight Grand Prix Bracket
** = Replacement