Celta are just one place and one point above the drop zone having managed a solitary victory in Spain's top flight in 2020-21.
A 1-1 draw at Elche proved to be Oscar's last game in charge, bringing an end to a year-long stay for the 47-year-old at Celta.
"Oscar Garcia Junyent and his coaching staff will no longer coach RC Celta," a club statement read.
"The club conveys its sincere gratitude, both to the Catalan coach and to his team, for the work, professionalism and effort they've shown throughout their time at RC Celta, in which they managed to consolidate LaLiga status during a complicated 2019-20 season.
OFFICIAL 🚨 Oscar Garcia will no longer manage RC Celta. The club wishes him all the greatest success in the future. pic.twitter.com/Hx56g6CS54— RC Celta English (@RCCeltaEN) November 9, 2020
"RC Celta wishes Oscar Garcia and his assistants the best of success in the future, both professionally and personally."
Oscar took over 12 months ago with Celta in the bottom three and managed to secure their status in LaLiga despite failing to win any of the last seven matches in 2019-20.
A nomadic coaching career has seen Oscar have stints at Maccabi Tel Aviv (twice), Brighton and Hove Albion, Watford, Salzburg, Saint-Etienne and Olympiacos.