While President Obama has had a presence on Twitter for quite a while via Obama for America/Organizing for Action's @BarackObama account, today the president officially joined Twitter with his own personal account, @POTUS. Previously, any tweets from the @BarackObama that were actually from the president (as opposed to OFA staff) were signed "-bo."
Hello, Twitter! It's Barack. Really! Six years in, they're finally giving me my own account.— President Obama (@POTUS) May 18, 2015
The first five people Obama followed on Twitter were the White House (@WhiteHouse), his wife Michelle (@FLOTUS), Joe Biden (@VP), Josh Earnest (@PressSec), and Valerie Jarrett (@vj44).
As of this writing, Obama has followed former presidents Bill Clinton and George H.W. Bush (George W. Bush is not yet on Twitter), but has not followed Hillary Clinton. @POTUS acquired over 70,000 Twitter followers within 20 minutes of its creation.