With Cristiano Ronaldo again sidelined with an ankle injury, Welsh star Bale stepped into the limelight with two first-half strikes to push his case for a starting spot in the European showpiece against Liverpool in Kiev in two weeks’ time.
Bale opened his account after 13 minutes on Saturday, picking up a sweetly-timed through ball from Luka Modric to score.
His second on the half-hour mark saw him dash to the byline before tucking the ball to one side of a defender and then unleashing a sharp left-footed drive into the corner of the net.
Bale celebrated by dedicating his performance to his third son Axel Charles who was born on Tuesday.
Isco made it 3-0 after 32 minutes before Moroccan midfielder Achraf added the fourth, seven minutes into the second half.
On a miserable night for mid-table Celta, Sergi Gomez put through his own net on 74 minutes, leaving German internatonal Toni Kroos to tuck away Real’s sixth goal after 81 minutes.
Real stay in third place in the table on 75 points, 15 behind champions Barcelona and three back from city rivals Atletico with one game left to play.
Earlier Saturday, Koke’s early goal proved enough for Atletico to claim a 1-0 win at Getafe and remain on course to finish in second place.
Atletico goalkeeper Jan Oblak also saved a late penalty from Faycal Fajr as Diego Simeone’s men warmed up for Wednesday’s Europa League final against Marseille by denting Getafe’s hopes of playing continental football next season.
The capital club got off to a quick start in the local derby, as Koke collected Antoine Griezmann’s pass and drove a low shot into the bottom corner to score his fourth goal of the campaign in the eighth minute.
Getafe missed a chance to stay just two points adrift of seventh-placed Sevilla in the chase to qualify for the Europa League, as Fajr’s 77th-minute spot-kick was kept out by Slovenian Oblak.
Simeone admitted the challenge posed by Marseille would be different to that encountered at Getafe.
“We will face a team who are very enthusiastic, with very good attacking players. They are a team that work well at the tactical level,” said the Argentine.
Sevilla would have wrapped up a top-seven finish with victory in their derby at Real Betis, but Loren’s equaliser with nine minutes to play snatched the home team a 2-2 draw.
Managerless Sevilla, who reached this season’s Champions League quarter-finals, now have to beat Alaves next weekend to secure a spot in Europe’s second-tier competition.
Elsewhere, Samu Castillejo scored twice as Villarreal beat relegated Deportivo La Coruna 4-2 to leapfrog Betis into fifth, with Denis Cheryshev also netting a day after being recalled to the preliminary Russian World Cup squad.