Richardson will portray Catherine Parr, Henry VIII's sixth and last wife, in five episodes of the 16th century-set series, which is currently filming in Dublin, Ireland.
Jonathan Rhys Meyers plays Henry in the show.
The new season of the series is slated to premiere next year.
Best known to American audiences for her celebrated work during five seasons on TV's "Nip/Tuck," Richardson is part of an English theatrical dynasty that includes her actress mother Vanessa Redgrave, director father Tony Richardson, actress aunt Lynn Redgrave and actress sister, the late Natasha Richardson.
Her film credits include "The Patriot," "I'll Do Anything" and "The Last Mimzy."