Yes. Simply.

William the Conqueror's son, Henry I, married his daughter Matilda to Geoffrey Plantagenet, Count of Anjou. After his son and heir died, Matilda became the heir to the throne, and the line continued with the Plantagenets until 1485.

So William the Conqueror's granddaughter, Matilda, was the great-great-great-great grandmother of Edward III.