Kim Kardashian hit up the Fifteen Percent Gala in Los Angeles ... and, she brought 100% of her style -- stunning in a gorgeous black gown.

The reality television star turned fashion mogul pulled up to the event Saturday night ... a gala in support of the Fifteen Percent Pledge -- a promise businesses make to ensure at least 15% of the products on their shelves are from Black-owned businesses.

As soon as she arrived, KK was surrounded by photogs ... who took a series of photos of her gorgeous gown that ya gotta see for yourself.

Kardashian wore an all-black dress with sheer material around her hips ... and, when she turned, she revealed the entirety of her back to the cameras.

Kardashian's dress only barely contained her famous backside ... and, almost certainly captivated the assembled crowd.

Worth noting ... Kim has a personal connection to the Fifteen Percent Pledge -- 'cause Emma Grede, a founding partner in Kardashians' SKIMS, is the Chairwoman of the project.

Grede cohosted last night's event with the pledge's founder, Aurora James, actress Tracee Ellis Ross and designer Brandon Blackwood.

Kim's clearly supporting a good cause -- and, looking way better than good while doing it.