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. An official speech is expected soon.
Iraqi forces have been battling the remaining pockets of jihadists desperately holding out in a tiny area near the Old City.
Sporadic bursts of gunfire could still be heard on Sunday, and plumes of smoke rose into the sky.
Thirty IS militants were killed as they attempted to escape the advance of the Iraqi forces by throwing themselves in the River Tigris, state media said.
The government announced the full “liberation” of eastern Mosul in January, but the west of the city, with its narrow, winding streets, has presented a more difficult challenge.
Some 900,000 people have been displaced from the city since 2014 – about half the the pre-war population – aid organisations say.
The Islamic State group has lost large parts of the territory it once controlled in Iraq since the regional offensive began.
But the fall of Mosul does not mean the end of IS in the country, as it still has territory areas elsewhere and is able to carry out bombings in government-held areas.
French President Emmanuel Macron was among the first to hail the victory of Iraqi forces in Mosul on Sunday, praising the fighters – including French troops in the coalition – who had made it possible.
Analysis: Victory at a terrible cost
By Alan Johnston, BBC World Service Middle East editor
The army has avenged its humiliating defeat by the militants in Mosul three years ago. But victory has come at a terrible cost.
Thousands of civilians have been killed. Much of Mosul has been destroyed.
And the dangers posed by the Islamic State group are not at end.
The militants will go underground and they may well look to make hit-and-run attacks in classic guerrilla style – in Mosul and many other places.