The club, who sit 14th in La Liga on 34 points, will replace Neville with his assistant coach Pako Ayestaran until the end of the season.
“Valencia have today rescinded their contractual relationship with Gary Neville as first team coach,” said a club statement.
“After carefully analysing the sporting situation, the club have decided to make this change in the best interest of Valencia Football Club from now until the end of this season.
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"The club thanks Gary Neville for his work and wishes him the best luck in the future.”
Neville was announced as the shock successor to sacked coach Nuno Espirito Santo last December.
In his 16 La Liga games in charge, Neville managed just three league wins, over Espanyol, Malaga and Granada, eight defeats and five draws.
His team reached the semi-finals of the Copa del Rey but were humiliated 8-1 on aggregate by Barcelona and were knocked out of the Europa League's last 16 by fellow Spaniards Athletic Bilbao on away goals.
Ayestaran was assistant coach to Rafael Benitez at Valencia between 2001 and 2004, helping the club to the La Liga title in 2002 and 2004 and the 2004 UEFA Cup.
He rejoined Valencia’s coaching staff in February at Neville’s request.
Gary’s brother Phil, who joined Valencia as assistant coach last year, is to remain at the club.
(Reporting by Richard Martin; Editing by Toby Davis)
