Whoa! Just, whoa!

Our dreams have come true, as Justin Bieber has FINALLY posted a nude selfie on Instagram! Frankly, we don't really care where he is or what he's doing -- only that his naked butt is gracing the homepage of X17online, BUT in an effort to flesh out this story a bit ... we're guessing he stopped in Fiji or in Tahiti on his way back from the Hillsong church conference in Sydney, Australia.

The Biebs spent some quality time with celeb pastor/pal Carl Lenz and his girlfriend -- friend who's a girl -- Hailey Baldwin. Wonder if the "it-girl" model's with Justin now!