Derby County have triggered a release clause in Tom Ince's Hull City contract to sign the winger for a club-record fee.
The 23-year-old joins Derby on a four-year contract after impressing on loan with the Rams last season.
He scored 11 goals in 18 appearances for the Championship side and now becomes their sixth signing of the summer.
New Derby head coach Paul Clement told the club website: "I'm aware of the positive impact he had on the side during his time on loan last season from speaking to people at the club, and also watching a number of the matches back myself.
"He is an exciting talent, there's no doubt about it, and he's another very positive addition to the squad."
Rams president and chief executive Sam Rush admitted that the fee paid for the winger, believed to be around £5m, was a "significant outlay" for the club.
Ince leaves Hull after just one season. He appeared three times at the start of last season's Premier League, but could not hold down a place and was first sent to Nottingham Forest on loan before enjoying a more successful spell with Derby.
