The 22-year-old scored three times in 13 appearances for Sheffield Wednesday last season, having previously failed to find the net in injury-disrupted spells with Wigan and QPR – all three clubs having been in the second tier when Keane joined them.
Keane has appeared just once for his parent club, as a substitute in 2011, but former United defender Rio Ferdinand said on Twitter: “Good luck to #WillKeane at Preston.. #WillScoreGoals”.
North End manager Simon Grayson said: “We are delighted to have signed Will. He has got fantastic movement and he is a goalscorer.
“He suffered a bad injury a few years ago, but he is hungry and after meeting him he ticks every box we are looking for.
“We have pulled off a bit of a coup beating several other Championship clubs to him and I do feel he is going to be a major asset to our squad.”
Keane joins Jermaine Beckford, scorer of a hat-trick in the Sky Bet League 1 play-off final at Wembley, and League 1 player of the year Joe Garner as attacking options for Grayson, who also acquired Paul Gallagher on a permanent basis after he contributed 16 assists in the league as a loanee last term.
“I’m really excited to be here and I’m looking forward to the new season and the challenge ahead,” Keane said.
“I want to come here and do my best to help the team. They had a very successful year last year and hopefully the whole club and the team can build on that this season.”
His arrival adds extra spice to the Lilywhites’ derby games with Burnley as his twin brother Michael is on the Clarets’ books.
The two have faced each other before, in 2014, when Michael’s Blackburn claimed a 2-0 victory over Will’s QPR at Ewood Park.