Aldon Smith cut a plea deal in his DUI case on Thursday morning, TMZ Sports has learned ... and the ex-NFL star is now facing prison time over it.
The San Mateo County District Attorney tells us ... Smith agreed at a hearing in Northern California to enter a plea of nolo contendere to a felony charge of drunk driving causing injury.
In exchange, the court agreed it would not impose a sentence on him higher than 16 months in state prison.
The DA noted probation and a county jail sentence are also on the table for Smith following the plea agreement.