Mariah Carey's Las Vegas outfit is definitely a hole-in-one ... 'cause she wore a skintight outfit to tee off at Top Golf!

The singer-songwriter shared a series of snaps highlighting her clothes to Instagram ... leaning on a golf club and ready to whack one a couple hundred yards.

MC shared a couple other pics too ... and, she's looking glamorous in each one with her mesh bodysuit -- which gives fans a glimpse of her bra -- and high heels.

She captioned the photo set, "Reinventing golf attire" ... we don't know if this classy ensemble will be emulated on many courses around the country -- but, never say never.

If you don't know ... Mariah's been in Vegas recently as part of "The Celebration of Mimi" residency which was supposed to end last year though more dates were added because of the high demand.

"The Celebration of Mimi" wrapped up February 15 ... so, it's unclear if Mariah's still in Vegas or if she's just sharing some of her favorite moments from her time in Sin City.

Mariah had a super popular tour in the lead-up to Christmas too ... and celebs seemed to love it as much as her other fans, 'cause  Rihanna wanted her boob signed after one show.

Looks like she's taking it easy after months of performing ... and, she may even be 'obsessed' with a new sport!