The Blades have added Premiership experience to the midfield ranks at Bramall Lane.
Leicester City's Dean Hammond has signed an emergency loan until January and is eligible to make his debut in Tuesday's Sky Bet League One clash against Fleetwood Town.
Hammond, who has won promotion from League One and the Championship, has over 400 senior appearances to his name, mainly with Brighton and Hove Albion and Southampton, for whom he played under the leadership of Nigel Adkins.
On the capture of Hammond, the United boss commented: "Dean is a fantastic professional, he was my captain at Southampton when we won promotion to the Championship and Premiership and he has enjoyed success with Brighton and Leicester.
"I cannot speak highly enough of him as a player and a person, he sets high standards both on and off the pitch and after waiting for the right person, we are delighted that we can bring Dean into this Football Club."
Hammond, 32, was on the bench for Leicester City's first Premiership game of the season and captained the Foxes in their Capital One Cup victory over Bury at Gigg Lane in August.
Last season the midfielder made 12 top-flight appearances as City produced a notable revival to avoid relegation.