Katherine Elizabeth "Katie" McGrath (born c.?1983) is an Irish actress who is best known for portraying the Lady Morgana Pendragon on the BBC One show Merlin from 2008 to 2012. McGrath is currently the star of horror television series Slasher.
McGrath was cast in Damage, an Irish TV-movie in 2007. She also starred in Bedrock Productions's play La Marea at the Dublin Theatre Festival 2007. She appeared in the feature films Eden and Freakdog in 2008, before being cast in Merlin.
In 2009, McGrath starred in a five-part docudrama for Channel 4 exploring the life of Queen Elizabeth II, The Queen, in which she played a young Princess Margaret. Emilia Fox portrayed Elizabeth II in the same episode McGrath acted in, the two had previously worked together as sisters Morgause and Morgana in Merlin. In 2010, McGrath was cast in Madonna's directorial debut W.E., an Edward VIII biopic. McGrath played Lady Furness, the king's former mistress who introduces him to Wallis Simpson.