The 28-year-old Jamaica international completed a medical with the club on Wednesday and was due to be unveiled on Thursday afternoon.
King is manager Phil Brown's eighth new signing ahead of the Tigers' first Premier League season.
Wigan boss Steve Bruce said: "We wish Marlon all the best. He is a good pro and he made a contribution last season.
"He has worked hard in pre-season and has made an impact, but he has chosen to move on for the time being."