Rihanna looked a hot mess this summer

Remember the days when Rihanna always looked killer? We do, too — so what happened this summer?

At some point in the last few months, the singer entered an experimental phase seemingly hinged on caring as little as possible. Ri, we feel you — but please, get off Tumblr. It’s not your best look.

Still, she wasn’t alone in her missteps — and on the flip side, plenty of stars didn’t let the oppressive heat impair their decision-making skills.

Here, let’s review the style — and lack thereof — we’ve seen from celebrities this season.

Best off-duty: Diane Kruger

On Sept. 1, the German actress won best-dressed before she even hit the Venice Film Festival red carpet. This is how you make an entrance: in a whimsical Thakoon dress, styled with a hat, shades and Chanel bag.

Best wow: Caitlyn Jenner

The Atelier Versace dress Jenner chose for her big ESPY Awards moment on July 15 was as well chosen as the words in her lovely speech.

Best sparkle: Cara Delevingne

“Paper Towns” may have been meh, but the film’s star shone in Saint Laurent at the New York premiere.

Best under-18: Elle Fanning

She had some stiff competition from Hailee Steinfeld all summer, but at the opening night gala of “Tig” in Los Angeles, the 17-year-old actress pulled through to first place in this (wildly popular) Prada dress. Seriously, how cute is she?

Best black: Alicia Vikander and Olivia Palermo

It’s a tie! At the “Ingrid Bergman – In Her Own Words” Stockholm premiere on Aug. 24, Vikander was a minimalist vision in Victoria Beckham. The dress was as good as — but opposite — the dramatic Valentino number Palermo wore to the brand’s Paris couture show on July 9.

Worst ‘best’: Emily Ratajkowski

For the “We Are Your Friends” premiere in France on Aug. 12, the rising star decided to wear . . . this. Sorry, but this looks like a “Sexy Christmas Tree” costume they’d sell at Party City.

Worst patriot: Kesha

July 5, 2015: a day that will live in fashion infamy.

Worst judgment: Jessica Stam

Nope — still not clothes!

Worst under-18: Bella Thorne

We don’t care if it’s the Teen Choice Awards and all the other kids are doing it — Bella, you’re 17! There’s no reason your dress should be so short and so tight (let alone match your hair and spray tan).

Worst overall: Rihanna

Did we lie?