The Blades have completed a fourth summer capture with George Baldock agreeing and signing a three-year contract at Bramall Lane.
An undisclosed fee with MK Dons has been confirmed for the defender's services and boss Chris Wilder is delighted with the latest addition.
Boss Wilder commented: "George is another to fit the bill of the squad we are looking to build here at Bramall Lane. He is a great age and has great experience and will provide us with competition for places in an important part of the pitch. We've tracked him for a while, monitored his progress, and we're looking forward to working with him when we return to pre-season training later this month."
Baldock, meanwhile, told sufc.co.uk: "I'm absolutely delighted to have signed and committed my future to this impressive club.
"I was excited when I heard of United's interest, for a number of reasons, including the manager's record over the past couple of seasons and the passion of the fans when they travelled to Milton Keynes a couple of months ago."
Despite only being 24, Baldock has almost 200 career appearances to his name, mostly with MK Dons, for whom he progressed through their youth system, whilst he has enjoyed loan spells with Northampton Town and Oxford United. He played full games in both fixtures against the Blades last season.
Ched Evans, Nathan Thomas and Enda Stevens have all already been added to Chris Wilder's squad ahead of the Championship campaign, which kicks off in August.