The 55-year-old will take charge of team affairs and will be assisted by current first team coach Kevin Blackwell.
A statement from Leeds United plc to the Stock Exchange this evening said: "Following a meeting today between Trevor Birch, the chief executive and Peter Reid, it has been mutually agreed that Peter steps down as first team manager with immediate effect.
"While the board acknowledges that Peter did a sterling job for the club towards the end of last season in keeping United in the FA Premier League, it believes it must not allow this season to reach a point beyond which the club’s Premiership status comes under serious threat.
"The recent run of results has clearly been unacceptable. The board therefore concluded that it has a duty to act now.
"With effect from tomorrow morning, Eddie Gray will take over the duties of the first team manager on a caretaker basis, assisted by Kevin Blackwell, the chief coach.
"The process of identifying a longer term first team manager is under way and the board has a clear view of the credentials required of any candidate.
"Notwithstanding current financial constraints, United is determined to return to its place as one of the top clubs in England and is looking to appoint a new first team manager who will reflect this determination."