After the result was announced, Obama took to Twitter to write: "We're all in this together. That's how we campaigned, and that's who we are. Thank you. -bo."
He then posted a snap of himself and wifeMichelle Obama embracing, along with the caption: "Four more years."
The showbiz world was also quick to congratulate Obama, with long-time supporter Beyoncé - who also posted a snap of her completing her election card - writing: "4 more years", accompanying her comment with a snap of Barack kissing Michelle on the cheek.
Queen B also uploaded a picture of poking fun at Romney, which read: "Take that Mitches."
Rihannaexclaimed: "Put one in da air for the Prez!!!! Our dear Obama!"
Mariah Careywrote: "Incredible speech!!!!!! Watching in a room full of diverse people - all truly moved. Thank you America for President Obama - 4 more yrs."
Lady GaGa stated: "I just got off stage in Columbia!! Congratulations Mr President @BarackObama We are so proud to be American tonight! YES!!! YES! YES!! We just couldn't be happier my goodness, the joy when freedom prevails."
Pic: Twitter @ladygaga
Kelly Osbourne claimed: "Thank God #Obama2012 has victoriously won I feel safer now there hopefully wont be a world war III & gays can finally get married! #victory."
Justin Bieber added: "A lot of emotions right now. congrats President Obama... I'm Canadian. I'm good. #FreeHealthcare :)"
ActressEva Longoria said: "Amazing speech by @BarackObama re-elected for his 2nd term! America is and can be united for the greater good of all Americans!"
The UK's very own Ricky Gervais tweeted: "Well Done America. We knew you'd get it right. #ObamaWins"
Whoopi Goldberg commented: "I'm so happy, now that it appears Prez.Obama has won will all you racists & nasty vitriolic angry folks go away & take your crap [with] you. We as Americans have work to do & we dont have time 4 bulls**t & we don't have time 4 ur bulls**t.Prez.Obama won & crying foul ain't gonna fly."
Ricky Martin posted: "Mitt, remember that 47%? #4moreyears #Obama2012"
However, not everyone was pleased with result, with business tycoon Donald Trump taking to Twitter to rant: "Well, back to the drawing board! He lost the popular vote by a lot and won the election. We should have a revolution in this country... This election is a total sham and a travesty.
"We are not a democracy! Our country is now in serious and unprecedented trouble...like never before. Our nation is a once great nation divided! The electoral college is a disaster for a democracy."