O-Town's Ashley Parker Angel Finally Just Gets Totally Naked

After teasing fans for months with half-naked underwear selfies, the O-Town stud took it all off on Instagram on Thursday -- and showed his followers all his hard work (and backside) from his recent fitness kick.

"The #100DaysOfFitness challenge may be behind me now but the journey continues. It's incredible how the human body responds and transforms to even just 100 days of a consistent diet and exercise program. During the last 100 days your positive comments motivated me to push through and stay committed," he wrote.

"I encourage all of you to experience for yourself how rewarding it is to set your own goals and get inspired by the results. You don't have to be a fitness model or featured in the ESPN Body Issue to be proud of your physique. We all have what it takes to be the best version of ourselves we can be. Be dedicated, be passionate and be relentless in the pursuit of your dreams. Shortly, you will look back at where you started and be astounded at how far you've come... and you might just be inspired enough to post a naked picture of yourself on Instagram. #Day100."

In the snap the 33-year-old showed off his muscular bod as he flashed the camera his very toned derriere!

And we must say ... that's one impressive body of work.

While the heartthrob is putting a lot on display here, he's no stranger to showing skin.

Back In February, the star posted another super sexy pic where he posed completely naked in a bathroom mirror, covering up his goods with a strategically placed white towel.

And while the former boy bander has been working on his fitness, his former O-Town band mates have been busy filming Nick Carter's "Dead 7" with members from the Backstreet Boys, *NSYNC and 98 Degrees.

"Getting ready for a boy band throw down! @Trevor_Penick @JeffTimmons @realjoeyfatone @skulleeroz," O-Town member Jacob Underwood said of an on set photo with his costars.