Kat Stickler's proving single life ain't all that bad ... 'cause she's living it up months after her breakup from former 'Bachelor' star Jason Tartick.

The YouTuber and influencer is regularly hanging out in tropical locales ... seen here lying back in an orange bikini on a recent trip down to Mexico.

Orange might be the new black ... but, sometimes the old black is just as good -- so, Stickler's also got this tiny bikini which she's featured in some of her other IG posts.

And, whether on vacation in places like Puerto Vallarta or hanging out in L.A. ... Kat's always ready to pose for a shot -- proving all angles are her good angle.

Like we said ... Kat and her ex Jason split back in October after about six months. While they're no longer together, the split appears amicable -- 'cause both said they wish the other best after it just didn't work out.

Despite the split, it looks like Stickler still living her best life ... and wearing a whole lot of gorgeous outfits to boot!