Iraqi PM Haider al-Abadi has arrived in Mosul to congratulate Iraqi forces for their victory over IS in the city.
Mr Abadi was in the city to announce its "liberation" and declare "victory", his office said in a statement.
Iraqi forces, backed by US-led air strikes, have been battling to retake Mosul since 17 October last year.
Islamic State militants seized it in June 2014 before taking much of Iraq's Sunni Arab heartland and proclaiming a "caliphate" straddling Iraq and Syria.
Kurdish Peshmerga fighters, Sunni Arab tribesmen and Shia militiamen have also been involved in the battle.
The Iraqi prime minister arrived to "congratulate the armed forces and the Iraqi people" on the final defeat of IS in Mosul on Sunday, the statement said.
Iraqi forces had been battling remaining pockets of jihadists desperately holding out in a tiny area near the Old City.
The government announced the full "liberation" of eastern Mosul in January, but the west of the city has presented a more difficult challenge, with its narrow, winding streets.
Some 900,000 people have been displaced from the city since 2014 – about half the the pre-war population – aid organisations say.