Valencia have sacked head coach Marcelino and have replaced him with former Real Madrid assistant Albert Celades.
Marcelino was dismissed following a reported falling out with club owner Peter Lim. Former Barcelona midfielder Celades, who took his first training session on Wednesday, has joined the club until June 2021.
In an official statement, the club said: "Valencia CF announced on Wednesday to Marcelino García Toral his dismissal as coach of the first team.
"The club wants to thank you for your work and dedication during your time in our entity and wish you the greatest success for the future."
Marcelino was appointed as Valencia boss in May 2017 but his position came under threat 12 months ago after a difficult start to the 2018-19 season.
However, the club kept faith in the former Villarreal boss and were rewarded when they ended the season by winning the Copa del Rey final against Barcelona and securing a Champions League spot.
Valencia have taken four points from three games this term and it was reported in Spain that Lim called club president Anil Murthy for an emergency meeting in Singapore on Wednesday after deciding to sack Marcelino.
Former Spain U21 coach Celades, who was also assistant to Julen Lopetegui at Real Madrid, is stepping into his first senior role in the dugout.
Valencia play Barcelona at the Nou Camp on Saturday, before facing Chelsea in their opening game of the Champions League on Tuesday.