We've learned ... 65-year-old Struthers was busted at 12:30 AM for OUI -- operating under the influence.
Struthers -- who starred in "All In the Family" before becoming a spokesperson for ChildFund International -- was released shortly after she was taken into custody after posting $160 bail ... which is just one dollar a day for the past 160 days.
Sally was handcuffed at the scene and law enforcement tells TMZ ... she was cooperative.
We're told drugs were NOT involved.
Struthers has been in Maine starring in the play "9 to 5."
The punishment for a first offender is a $500 fine and a 90-day license suspension. There is no risk of jail time.
Struthers' arraignment is set for December 14.
2:44 PM PT -- A rep for Struthers released a statement saying, "Sally is working and she is fine and she loves The Ogunquit Playhouse and her yearly time in Ogunquit. We deny these charges."