The SKIMS founder dumped a bunch of pics of herself out with sister Khloe Kardashian and mom Kris Jenner ... but the real star in the snaps is that 'fit! Kim and co. caught one of Janet's SoCal shows last week, and while thousands of fans cheered on the icon, only Kim was rocking an iconic look!

For the evening out, Kim wore the outfit made famous by Janet in her “If” music video – black crop top with white boning, lace-up black pants, etc. -- which the reality TV star bought at an auction for $25,000 a while back.

Kim shared a closer look at her evening out with family -- including a shot of her platinum blonde self posing next to Khloe, who wore a black catsuit along with black thigh-high boots.

In typical Kardashian fashion, Kim did an entire photo shoot with her auction-bought ensemble ... posing everywhere from a green room to a party bus to her seats in the venue.

She later filmed herself and Khloe singing along to Janet's hit, "Again," captioning the post ... "that’s the way love goes."

Fans couldn't get enough of Kim's escapade outing, applauding the look and the OG designer -- "It’s a vintage RIFAT OZBEK top kim should wear more of his stuff one of the most underrated designers ever 🔥."

KK's quite the memorabilia collector ... having previously purchased daughter North West the "Smooth Criminal" hat, once worn by Michael Jackson in his 1988 music video. She also once bought jewelry worn by the late Princess Diana and First Lady Jackie Kennedy.