Mieszko I (c. 935 – May 25, 992) was a duke of the Polans and the first historical ruler of Poland. He was father of Boleslaw I, first polish king.
Gallus Anonymus writes that Mieszko was blind until his 7th birthday. That information was used by later chroniclers, but it's probably just an allegory.
Mieszko was the first catholic ruler in Poland, he married Dobrawa of Bohemia and after that got baptised.