Simon Moore has committed his long-term future to the Blades, after the club turned down bids for the goalkeeper.
The 28-year-old stopper, who was instrumental in United's record-breaking Sky Bet League One title-winning campaign in 2016/17, has penned a new three year-deal, ensuring he is under contract at Bramall Lane until the summer of 2021.
Last season Moore overcame a knee injury in pre-season to compete for the number one jersey with Chelsea loanee Jamal Blackman and he made 19 appearances in all competitions.
Moore joined United from Cardiff City for an undisclosed fee in August 2016 and has made a total of 64 appearances as a Blade.
Boss Chris Wilder remarked: "Simon was coming towards the end of his contract, so we're delighted to tie him down because he's done fantastically well for this football club. We need competition in that department and we're fortunate to have three goalkeepers in Dean, Simon and Jake that are all pushing each other."
On committing his future to the Blades, Moore added: "My most enjoyable years in football have come at this club and I'm proud that I can continue to be part of that in the future.
"It's a special dressing room and a great bunch of lads. The demands the manager puts on everyone brings the best out in individuals and I'm relishing the challenge ahead."