Khamenei "has approved... pardons and sentence reductions for 3,458 people convicted" by various Iranian courts, a statement said.
The measure, at the suggestion of the head of the judiciary, coincides with the anniversary of the Prophet Mohammed's birth, and that of Imam Sadegh, one of the most holy figures in Shiite history.
Iran marks the birth of both on Sunday.
Iran's supreme leader routinely grants collective pardons on major religious holidays, in coordination with the head of the judiciary.
In late July, Khamenei pardoned or reduced the sentences of more than 2,800 detainees.
