The judge, Army Col. Denise Lind, handed down the sentence at Fort Meade, outside Washington. She also ordered that Manning, the army intelligence analyst, be reduced in rank to private and be dishonourably discharged from the army, Xinhua reported.
Manning, now 25, could face a maximum of 90 years in prison. He was convicted of several charges last month, including espionage and theft. But the judge found him not guilty of the most serious charge, aiding the enemy, which possibly carried a life term in prison.
Manning was accused of delivering to WikiLeaks three-quarters of a million pages of classified documents and videos, which covered numerous aspects of US military operations in Iraq and Afghanistan and US diplomatic missions across the world.
WikiLeaks, though, has never confirmed Manning as the source of its information.
Manning was arrested months later after one of the leaked videos appeared on WikiLeaks in April 2010. It was a gunfire video of a US attack helicopter firing at a group of people in Baghdad in 2007.
WikiLeaks, an international organisation that publishes secret information and news leaks from anonymous sources, continues to publish documents related to the 2010 Afghanistan war, the Iraq war Logs and diplomatic cables by US State Department officials.