The Sky Bet League One side moved to end the former Scotland internationalist's tenure just three months into the campaign after a team touted for promotion won just one of their first 10 league matches - and that on the opening day - to find themselves in the division's relegation places with just five points.
The former Rangers defender was only appointed in June but was told of the decision yesterday along with Lee Carsley, his assistant, who has also been relieved of his duties. Chief executive Julian Winter told the club's official website: "First and foremost all at Sheffield United, from the board right the way through the club, wish David and Lee all the best for the future. None of us wanted to be in this position at this point in the season. David's appointment was made as part of developing a new phase at the club."
Chris Morgan, the club's under-21 coach and former defender, will take charge on an interim basis with the help of goalkeeping coach Darren Ward and head of academy coaching Travis Binnion, with his first game being tomorrow's trip to Sixfields to face Steven Pressley's Coventry City.
The South Yorkshire club insisted last night that they aim to appoint a new permanent management team as quickly as possible. Winter added: "Chris Morgan has been asked and agreed to take an interim role in charge of Sunday's team. He knows the players and, with Darren and Travis, will be doing his utmost to get a return to winning ways."
Morgan added: "The club have made me aware of the situation and I am happy to step in and work with the players for the Coventry game."
Weir replaced Danny Wilson in the summer but endured a baptism of fire in his first management role, losing nine of United's 13 matches in all competitions. Saudi Arabian Prince Abdullah bin Mosaad purchased the majority of the club's shares from owner and chairman Kevin McCabe last month and gave Weir his full backing. Despite his support, the fans have consistently expressed their concern at the poor start to their third season in the third tier, which has seen United lose five of their last six games.