Sienna Tiggy Guillory (; born 16 March 1975) is an English actress and former model. She is perhaps best known for her portrayal of Jill Valentine in several entries of the Resident Evil action-horror film series. Other prominent roles include elf princess Arya Dröttningu in the fantasy-adventure film, Eragon, and the title role in the TV miniseries, Helen of Troy.
More recently, Guillory has taken on starring roles in popular TV shows including Fortitude, Stan Lee's Lucky Man and Luther.