Akon got locked up in Georgia after being arrested on a warrant ... but he's already been let out of jail.

The "Locked Up" rapper was busted in DeKalb County last Thursday ... the DeKalb County Sheriff's Office confirms to TMZ.

We're told the Chamblee Police Department arrested Akon in the morning on an out-of-county warrant, and he was booked into jail and released within 6 hours.

It's unclear what the arrest warrant was for ... we're working on it. Gallery Launch Gallery Getty

Akon -- government name Aliaune Thiam -- posed for a mug shot in jail ... he's wearing a black hoodie and is mostly expressionless.

We reached out to Akon's camp ... so far, no word back.

Story developing ...

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