The model/mogul posted several pics of her as the vintage character on her Instagram Wednesday morning ... first posing in a silver top with a white silk skirt -- and baring her toned stomach as she looks off into the distance.

Another shot captures the youngest KarJenner sister in a strawberry-blonde wig -- blaster in hand, elbow resting on a stocking-covered leg.

A final snap shows the star crawling on all fours in a black-and-white shaggy ensemble, complete with a tail and tall silver boots.

She captioned all three of her pics with just one word, "BARBARELLA," written in capital letters ... so, we have a feeling she's pretty darn excited about her costume.

If you don't know ... the movie "Barbarella" came out way back in 1968 and starred Jane Fonda as the title character. The film was mostly popular overseas -- and, was condemned by the National Catholic Office for Motion Pictures in the U.S. for its nudity and depiction of sadism.

Paramount is now rebooting the flick ... which is set for release next year and will star Sydney Sweeney as Barbarella. Fonda has already said she's worried about how the new movie will come out.