The Sheffield star steps up from welterweight to face WBC, IBF and WBA middleweight champion Gennady Golovkin at the O2 in London.
Brook, 30, believes he will become the pound-for-pound king of the sport if he dethrones the Kazakh.
Golovkin ? who has won 32 of his 35 fights by stoppage ? is regarded as one of the best in boxing.
Russian light-heavyweight Sergey Kovalev and American Andre Ward ? who face each other in November ? and Nicaraguan super-flyweight Roman Gonzalez challenge Golovkin for the accolade of pound-for-pound best.
But Brook ? who will pocket around ?3m for the fight – is sure he will be crowned the new No.1 in front of a sold-out O2.
He said: ?I will definitely be pound-for-pound the best.
?I?m coming up two weight divisions and this fight is going to be unbelievable. This will put me right up there as No.1 pound-for-pound.
?The only thing that is stopping me from sleeping is thinking about having that title and becoming the best in the game.?
Golovkin is the biggest foreign name to fight in the UK since Russian-born Australian Kostya Tszyu fought Ricky Hatton in Manchester back in 2005.
