The Blades have fought off competition to land the services of Oxford City striker Horatio Hirst.
The 18-year-old has penned a one-and-half year development contract with United and will be eligible to feature for both the U18s and U23s.
Hirst has completed a successful trial period at the SteelPhalt Academy at Shirecliffe, having caught the eye during City's FA Youth Cup campaign where they beat Peterborough United en route to the third round.
On the signing of Hirst, Academy boss Travis Binnion remarked: "Horatio is a promising striker who we feel has the potential to improve and progress further with hard work.
"He will begin with Del (Geary) and the U18s and will need to perform well there in order to earn opportunities in the U23s."