Fiona Mary Shaw, CBE (born Fiona Wilson; 10 July 1958) is an Irish actress and theatre and opera director, known for her role as Petunia Dursley in the Harry Potter films and her role as Marnie Stonebrook in season four of the HBO series True Blood (2011). She has worked extensively with the Royal Shakespeare Company and the National Theatre, twice winning the Olivier Award for Best Actress; for various roles including Electra in 1990, and for Machinal in 1994. She won the 1997 Drama Desk Award for Outstanding Solo Performance for The Waste Land. Her other stage work includes playing the title role in Medea, both in the West End and on Broadway (2001–02). She was awarded an Honorary CBE in 2001.