"Diamantino" follows a preening metrosexual goal machine with a fondness for displaying his waxed torso at every possible occasion.
But the eponymous hero's life falls apart when he misses a penalty in the World Cup final for Portugal on the same night his father dies.
Every time he bears down on goal afterwards he is haunted by images of gigantic pink Pekingese lapdogs blocking his way.
Having lost his killer touch, his career ends in disgrace.
Desperate to rebuild his life, the star "sets out on a delirious odyssey where he confronts neo-fascism, the refugee crisis, genetic modification, and the hunt for the source of genius," said the film's co-director Gabriel Abrantes.
Critics have cheered the debut feature – which also has subplots about the Panama Papers and gay adoption – as a hilarious Portuguese cross between John Waters, Pedro Almodovar and Monty Python films.
The Hollywood Reporter raved that "what makes 'Diamantino' such a gem is that it is not only a completely wacky story filled with the most improbable B-movie tropes... and a constant barrage of unexpected twists and turns", but that it also had important things to say.
"It's a Trojan Horse of a movie, smuggling in big ideas on the backs of gigantic lapdogs in fluffy pink clouds involved in one of the wackiest plots you've ever heard or seen.
"Finally, you can have your B-movie cake and eat it with grade-A ideas," said critic Boyd van Hoeij.
With side stories about an attempt to clone the player by shady scientists and the Ronaldo figure falling for his adopted son who is really an undercover lesbian cop, he said the film was sure to inspire "a raft of queer-studies theses".
The movie's American co-director Daniel Schmidt said it was the underlying innocence of the Ronaldo character that holds the mad romp together.
"I think the chaos of today is mirrored in the film. Like any good fairy tale, I hope it entertains while offering a new perspective on what's happening in the world. Diamantino's innocent perspective links it all together."
Ronaldo's Real Madrid teammate Keylor Navas, known as "God's Goalkeeper" for his strong Christian faith, is expected to attend the world's biggest film festival Sunday.
He will promote a new documentary about his time with the Champions League holders.
Navas was the hero of another film last year, "Man of Faith", made in his native Costa Rica.