The capture of Palestine Bridge, straddling the Euphrates river in northwestern Ramadi, means Iraqi forces have the city surrounded. They will now move to clear the city of the militants one neighborhood at a time.
"The bridge is now entirely under our control," said Sabah al-Numani, spokesman for the Iraqi counter-terrorism forces, which are deployed on the western side of the bridge along with federal police.
"We are tightening our grip on them (ISIL)."
Ramadi, the capital of Anbar province, fell to ISIL in May.
An army colonel from the 9th division, on the eastern side of Palestine Bridge, said that explosive disposal teams were preparing to clear the way.
"This advance is very important," said the colonel on condition of anonymity. "Daesh (ISIL) can no longer ferry weapons, food and equipment through the river like they did in the past," Reuters reported.
Retaking the city would be a major psychological boost for Iraqi security forces.
Defense Ministry spokesman Tahsin Ibrahim confirmed the bridge had been retaken, isolating ISIL militants inside Ramadi from their strongholds further west in Anbar province and Syria.
The ultimate goal for Iraqi forces is to break ISIL's grip over the northern city of Mosul. Kurdish forces recently recaptured the city of Sinjar in northwestern Iraq, cutting an important supply line between Mosul and the city of Raqqa in Syria.