Ms Park faced growing calls to resign amid an investigation into whether she allowed a long-time friend to influence political decisions for personal gain.
She said she would “leave to parliament everything about my future including shortening of my term”, but did not want to leave a power vacuum.
Parliament is due to discuss on Friday whether she should face impeachment.
Some in the ruling party had said the president should stand down “honourably” before it reached that point. Opposition parties accuse her of now trying to escape impeachment.