Olivia Culpo is baring it all in order to drum up interest in her upcoming clothing line ... rockin' nothing but a tiny bikini bottom in a steamy new ad.
Christian McCaffrey's fiancée posted the short commercial on her Instagram page Friday morning ... and, yeah, it's spicy, to say the least.
You can see the former Miss Universe champion sitting by a pool with her top off ... posing for a camera placed strategically behind her.