Captain Sharp, who scored 30 goals to help achieve promotion from League One last season, has signed a two-year deal with midfielders Coutts and Basham.
Full-back Freeman, 25, has penned a three-year deal after scoring 11 goals in 46 appearances in 2016-17.
"We cannot underestimate how important it is to have them on board," Sheffield United manager Chris Wilder said.
"We are looking for all four to step up a level and enjoy the challenges of the Championship."
All four players made over 40 league appearances each last season as Wilder's side finished on 100 points to move back into the Championship after six seasons in the third tier.
Billy Sharp, Paul Coutts, Chris Basham and Kieron Freeman have signed new contracts with Sheffield United.