Barca has won only two of their last seven league games under Koeman, a run that included losing to Real Madrid in Sunday's 'El Clasico' at Camp Nou.
Pressure had been building on the Dutchman since a 3-0 defeat against Benfica in Lisbon in late September, which made this season the club’s worst-ever start to a Champions League campaign.
A poor start to the season has raised the possibility of the team failing to qualify for next season's Champions League, which would have enormous consequences for the club's already-dire financial situation.
Barcelona's former midfielder Xavi Hernandez, who is currently in charge of Qatari club Al Sadd, and River Plate coach Marcel Gallardo are reportedly among those under consideration to take over.
A club statement released after midnight in Spain read:
"FC Barcelona has dismissed Ronald Koeman as coach of the first team tonight."
"The president of the club, Joan Laporta, has informed him after the defeat against Rayo Vallecano. Ronald Koeman will say goodbye to the squad this Thursday at the Ciudad Deportiva.
"The FC Barcelona wants to thank him for his services and wishes him good luck in his career."Back