Carlo Ancelotti’s side continued warming up for the Champions League final with a comprehensive demolition of their Basque visitors.
Bellingham scored the opener and played a part in Madrid’s next three goals, two scored by Vinicius, finding his best form at the business end of the season.
Turkish teenager Arda Guler added a late fifth to put the cherry on Madrid’s cake, moving them 17 points clear of second-place Barcelona.
“We’ve had just one defeat in the league and I think that a big part of the success is because of (the defense),” Ancelotti told reporters after his side’s 30th consecutive league game unbeaten.
Madrid celebrated their title with an open-top bus parade on Sunday but with the Wembley final a little over a fortnight away, nobody is letting their concentration slip.
Least of all Belgian goalkeeper Thibaut Courtois, made a fine double save from Samu Omorodion in the opening minutes.
After missing most of the season with a severe knee injury, Courtois is hoping for a Champions League final start and boasts three clean sheets in three matches since his return.
“I knew I’d come back strongly — I’m the same Courtois, or even better,” said the goalkeeper.
Ancelotti selected the vast majority of his first choice line-up after resting them at the weekend, and Madrid’s usual suspect opened the scoring. It was Bellingham, with his 19th league goal and perhaps his luckiest.
The England international directed Toni Kroos’ cross towards the far post where Dani Carvajal was running in, but the ball sank directly into the net.
Bellingham trails La Liga’s top scorer, Girona’s Artem Dovbyk, by one goal.
Madrid doubled their lead after Bellingham threaded a pass-through for Eduardo Camavinga.
The French midfielder burst forward in the box and unselfishly squared for Vinicius to tap home when other players might have taken the chance to shoot.
Alaves midfielder Ianis Hagi, son of legendary Romanian playmaker Gheorghe Hagi, stung the palms of Courtois with a fierce drive at the other end.
The visitors have enjoyed a strong season and are safely ensconced in mid-table, avoiding the stress of a relegation battle.
However, Madrid dismantled them with consummate ease and Fede Valverde rattled home the third in first-half stoppage time after Bellingham played him in.
The Uruguayan midfielder hammered a strike into the top corner at the near post for his second league goal of the season, far fewer than his tally of seven last year due to his deeper role.
Courtois denied Omorodion and Hagi again in the second half as he continued stating his case to Ancelotti, and he ended up making nine saves altogether.
Vinicius extended Madrid’s lead after Bellingham played him in, lashing home his second of the night with a fine finish.
“I’m at my best,” said Vinicius. “Now we’ve got time to train and that lets us stay calm, do good work and arrive better than ever at Wembley.”
Rodrygo should have added the fifth but goalkeeper Jesus Owono denied him from close range after Vinicius teed him up, and so it was Guler instead after a deflected effort fell his way in the box.
“Every time a small team comes here, it’s a torment,” lamented Alaves coach Luis Garcia Plaza.
Eder Militao and Carvajal ended the game with apparent physical issues, but they turned out to be nothing serious.
“What happened with the knee is nothing,” Militao said after the game, while Ancelotti confirmed the Spanish defender was also fine.
Elsewhere high-flying Girona, third, fell to a 1-0 home defeat against Villarreal Barcelona can move four points clear if they win at Almeria on Thursday.
Mallorca, 15th, rescued a 1-1 draw at Osasuna to add one more point in their battle for survival. The Copa del Rey runners-up are seven points clear of the relegation zone.