The Bristol fighter will bid for glory in front of a home crowd at the city’s Action Indoor Sports Arena on June 13.
Haskins (31-3) has won his last five fights, last time out taking the European bantamweight title when he stopped Omar Lamiri of France in the eighth round, and he has also held British titles at super-flyweight and bantamweight.
Ranked four by the IBF, he now takes on the body’s third-ranked fighter in Iwasa, whose 19-1 record includes wins over dual world title challenger David De La Mora and former WBC International champion Hiroki Shiino.
“It???s amazing to finally land this world title shot,” Haskins said. “At times I thought it would never come – when other British fighters I had beaten got their chances.
“And when the IBF announced I was to fight Ryosuke Iwasa, a Japanese fighter, I presumed we would probably have to travel to Japan. But massive thanks to promoter Mick Hennessy and my manager Chris Sanigar for bringing this world title to my hometown of Bristol.
“I know this is going to be a tough fight, but I???ve never lost in Bristol and, with that massive West Country support behind me, we can make history on June 13.”
Promoter Mick Hennessy added: “This is a major opportunity for Lee Haskins and one he has been chasing for a number of years now.
“He has more than paid his dues at the top of the bantamweight division and has beaten a number of quality operators throughout his career.”