"The civilian council of Raqa will be charged with administering Raqa and the surrounding province after liberation," the Syrian Democratic Forces said in a statement.
The council was announced during a meeting in Ain Issa, a former IS stronghold some 50 kilometres (30 miles) north of Raqa, in northern Syria.
The SDF launched an offensive to capture Raqa, IS's de facto Syrian capital, in November with support from the US-led coalition.
But a key question has been who will administer the city after its capture.
"The council is made up of people originally from Raqa province. (The SDF) will entrust it with the running of the city once IS has been pushed out," said Jihan Sheikh Ahmed, a spokeswoman for the Raqa campaign.
Several tribal chiefs and local dignitaries from Raqa participated in the meeting establishing the council, which mirrors others set up in towns captured from IS by the Kurdish-Arab force.
A military council will also be formed "soon", according to SDF spokesman Talal Sello, and charged with security in the city after IS is expelled.
"The SDF will train people originally from Raqa in cooperation with the international coalition to ensure the city's security after it is freed," Sello told AFP.
On Saturday, the SDF reached the outskirts of the key IS-held town of Tabqa, which they surrounded earlier this month.
Tabqa and the vast nearby Tabqa dam are considered key prizes in the broader offensive for Raqa city, about 55 kilometres to the east.
The SDF has led the fight against IS in large swathes of north and northeast Syria, with support from the US-led coalition.
But its advances have angered neighbouring Turkey, which views the Kurdish component of the alliance as an affiliate of the banned Kurdistan Workers' Party (PKK).
The dominance of Kurdish forces in the fight has also stirred ethnic tensions with Arab residents of the areas taken from IS.
Some three quarters of Raqa city's pre-war population was Sunni Arab.
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