The 63-year-old had been hoping to kick-start his career back in his homeland on the back of disappointing stints with the likes of Dalian Professional and Everton.
Benitez had also been in the managerial wilderness for the best part of 18 months before he was appointed as Celta Vigo boss in July 2023.
He had gone seven-and-a-half years without managing in his homeland, the Spaniard last in charge of Real Madrid up until the start of 2016.
However, the former Champions League-winning coach has departed Celta Vigo after just 33 matches in charge, prevailing on only nine occasions.
Perhaps more notably, 15 of those fixtures ended in defeat, including six of Celta's last nine in all competitions.
In Benitez's defence, his side had collected four points from matches against Cadiz and Almeira ahead of their trip to the Bernabeu to face Real Madrid on Sunday.
Nevertheless, a 4-0 loss has led to the powers-that-be at the 17th-placed club opting for a change in direction at Estadio Abanca Balaidos.
A club statement read: "Rafa Benitez and his staff leave RC Celta after eight months of absolute dedication and total commitment, but in which the team has not obtained the results expected by the club.
"The club would like to express to Rafa Benitez and his assistants its most sincere gratitude for the honesty and professionalism they have shown since their arrival and the tireless work they have done.
"RC Celta would also like to wish them the best of luck and success in the future."
Celta have sacked Benitez at a time when they sit just two points above the bottom three, with a meeting against potential relegation rivals Sevilla up next on Sunday.