The Midfielder who was targeted by other clubs has been in talks with the Bramall Lane club all week and signed a three year deal. The total transfer has cost the Blades 800k, though this could rise to 1M depending on appearances.
Neil Warnock told sufc.co.uk; "He's a player who has been top of my wanted list for some time and I have wanted to sign him for years. My disappointment at losing at Wolves has been tempered by still being able to sign Lilian, Paul and a few others."
"I believe he is the type of player we want, strong and quick, at a great age, and I also believe he could walk into a Premiership side already. It is hard to understand why big clubs haven't taken him on in the last couple of years, but it has turned out to our benefit."
"I think with Paul Ifill, along with Lilian Nalis and two or three others I want to bring in, supporters can see we are trying to bring in the quality needed to supplement what is already a very good squad - one to take us to another level.
"It's great for Sheffield United supporters to see the Club bringing in this type of quality because it shows just which direction the directors and I want the Club to go in."
The signing of Ifill comes just days after Neil Warnock brought in Frenchman Lilian Nalis from Leicester City on a free transfer.