She speaks his name.

Many times in this movie, she speaks his name — often in a moment of deep drama or intense crisis.

“Valerian!”

“Valerian!”

“VALERIAN!”

And every time she speaks his name, it is proof one can deliver a terrible performance in just four syllables.

Not to single out Cara Delevingne, the model turned actress who stars in “Valerian and the City of a Thousand Planets” and who is the one crying “Valerian!” throughout this movie.

Hers is not the only stiff acting job in Luc Besson’s bizarre and bloated and clunky pop sci-fi epic. Between Delevigne and her co-star Dane DeHaan, they’re so wooden they could have floated forever in the waters near the sinking Titanic and saved Rose AND Jack.

Also, Rihanna is in this movie as a sultry stage performer, and even when she is disguised in a variety of shape-shifting CGI personas, she does not give us a good performance either. It’s as if there was a Bad Acting Virus in the air on the sets of this film, and just about every performer involved was infected.

Based on a popular and long-running series of French comic books, “Valerian and the City of a Thousand Planets” pops with candy-colored visuals and begins with some promise: a centuries-spanning medley set to the tune of David Bowie’s “Space Oddity,” and a surreal, oddly beautiful scene on the planet Mul, where an androgynous-looking species exists in loving, peaceful harmony with nature — until a nearby war literally crash-lands on the beach.

For the remaining two hours-plus, “Valerian” is an excruciatingly repetitive, sparsely plotted, slow-witted, weird-for-the-sake-of-being-weird bomb. It has been said it takes a truly talented artist to make a truly memorable work of junk, and that certainly holds true here.

DeHaan, playing a Han Solo-type character with zero panache and making Harrison Ford look like he has the range of Daniel Day-Lewis, is the obligatory brave and talented but rebellious and reckless rogue agent with the United Human Federation (humans being just one of hundreds upon hundreds of species co-existing in the vast universe). Delevingne, all arched eyebrows and flat line readings, is his partner Laureline, a feisty and capable but more conventional operative.

Early in the story, Valerian proposes to Laureline. It comes out of the blue and seems so insincere we wonder if he’s joking. Laureline herself tells Valerian to slow down, as they hardly know each other. For much of the rest of the adventure, Valerian continues to express his love for Laureline and his intention to marry her.

It doesn’t come off as romantic. It comes across as light stalking.

Much of “Valerian” is set on Alpha, a huge metropolis containing species from, well, a thousand planets that live in one quadrant or another. The Human Federation’s Commander Fillitt (Clive Owen) sends Valerian and Laureline on a vital mission involving Melo, the only surviving creature from the long-extinct Planet Mul.

Let me tell you about Melo. He’s a cute little multi-colored CGI creature with large, sympathetic eyes and a sweet nature.

Melo has a very particular set of skills. If you feed him something — say, a magic pearl — he will almost immediately multiply that item a thousand times and send it right back into the world.

And know they don’t come up through his mouth.

Valerian and Laureline encounter all manner of strange and wacky creatures along their journey. One entity is vaguely reminiscent of Jabba the Hut. Some resemble certain droids from recent “Star Wars” films. A trio of duplicitous informers look they were just kicked out of the “Star Wars” cantina.

The “been there, seen that” visuals also bring to mind “Blade Runner,” the “Guardians of the Galaxy” movies and Besson’s own “The Fifth Element.” Sure, the pricey special effects are impressive to behold (though, as usually the case, the 3D is nothing to text home about). And yes, at times “Valerian” creates a strange and beautiful universe.

Which ultimately means nothing, because the plot is paper-thin, the big twist is obvious from the moment we are introduced to the character central to that big twist — and the two leads asked to carry the film deliver their lines as if they’re auditioning for a local theater group and they have no chance of getting a callback.

I’ve seen worse movies this year. I think.

★1⁄2

STXfilms and EuropaCorp present a film written and directed by Luc Besson, based on the comic book series “Valerian and Laureline” by Pierre Christin and Jean-Claude Mézières. Rated PG-13 (for sci-fi violence and action, suggestive material and brief language). Running time: 137 minutes. Opens Friday at local theaters.