"Gilbert Melendez is one of the toughest fighters on the planet," Henderson said. "I've said over and over that I just want to fight the best in the world.
"I don't care in what order I face them, but I want to fight the best in the biggest fights. He has been the Strikeforce lightweight champion, and is going to be real hungry in his first UFC fight."
Henderson (18-2) makes the third defense of the 155-pound belt he won on Feb. 26, 2012, with a unanimous decision over Frankie Edgar.
Melendez (21-2) made the final defense of his Strikeforce title on May 19 when defeated Josh Thomson by split decision.
He was scheduled to defend his belt on Nov. 3 against Pat Healy, but a shoulder injury forced Melendez to withdraw from the bout.
Cormier has stated on several occasions during the past few months that he wants to make his UFC debut against Mir.
The two were scheduled to meet Nov. 3 in a Strikeforce-promoted event, but the bout was scrapped after Mir suffered an injury.
Cormier hinted at a possible April 20 bout with Mir after his second-round TKO win Saturday night over Dion Staring in Oklahoma City.
"Most of the other [heavyweights] are tied up," said Cormier, 11-0 as a pro. "Everybody else is pretty much scheduled in the division. Why not [Mir]?
"We were supposed to fight already. It's a good fight. I think people would watch it and we can sell that fight."
Mir (16-6) has not fought since May 26 when he was knocked out in the second round by then-champion Junior dos Santos.
Hardy (25-10) is coming off a unanimous decision win over Amir Sadollah in September. The Brit is riding a two-fight win streak, a nice rebound from a previous four-fight skid. Now based in Las Vegas, Hardy is 6-4 in the promotion, including a 2010 title fight against Georges St. Pierre that he lost via decision.
Brown (16-11) also has revitalized his career as of late, winning four in a row. A former contestant on The Ultimate Fighter reality series, brown dropped four of five from 2010 to 2011 before starting his current streak. He most recently scored a second-round KO over Mike Swick in December.
ESPN.com's Brett Okamoto contributed to this report.