"In addition to their commitment to a seamless and safe convention, Philadelphia's deep rooted place in American history provides a perfect setting for this special gathering," DNC Chair Debbie Wasserman Schultz said in a statement.
Party nominating conventions are held after a long and sometimes grueling string of state primaries. The political parties formally christen their presidential candidates at the gatherings, but the contest is usually decided well before.
Former Secretary of State Hillary Clinton is seen as the front-runner for the Democratic nomination but has not formally launched a campaign. Vice President Joe Biden, senators Bernie Sanders of Vermont and Elizabeth Warren of Massachusetts, and former Maryland Governor Martin O'Malley also are often mentioned as possible candidates.
Former Senator Jim Webb of Virginia was the first to take serious steps toward running when he formed an exploratory committee in November.
Democrats held their 2012 convention in Charlotte, North Carolina. The national committee said it considered hotel capacity, transportation options, security and other logistics in choosing Philadelphia for the 2016 event.
"We're all delighted to make history again, here in the City of Brotherly Love and Sisterly Affection," Philadelphia Mayor Michael Nutter said in a statement released by the DNC.