The Take That star used just his hands to cover his modesty in the photo, which shows him proudly grinning while posing in a room.
Captioning the snap, Robbie asked his followers: "Do you think my bell-end can #BreakTheInternet on my birthday?"
The photo, which was shared just hours ago, so far has over 1000 retweets and 2000 favourites on Twitter. While over on Facebook, Robbie's snap has received 100,000 likes.
It appears fans were pleased with the photo, with one saying: "Certainly put a smile on my miserable face today!! Happy Birthday Mr W!"
Another wrote: "Oh my sweet lord!"
And one fan even compared Robbie's naked pose to Kim Kardashian's naked shoot for Paper magazine, simply saying: "Better than Kim."
This isn't the first time Robbie has sent social media into meltdown. In October last year, the 'Angels' singer and his wife Ayda kept fans amused by posting a series of funny videos and photos online while she was in labour.
Robbie and Ayda, who tied the knot in 2010, are parents to two-year-old daughter Teddy and three-month-old son Charlton Valentine.
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