Her father used to play guitar, while her mother was a model. She moved to Mexica at the age of 10 in order to learn Spanish. However, when she was 14, her parents got divorced. She studied at Gresham's School, where she took part in several dramas and plays. She started learning horse riding since she was only 2 years old. She even got her own horse when she was 14, which was christened “The Night Porter”.

She first started her career as a model. She visited with her friend the modelling agency Select in 1997, and was chosen to be their model. However, she later stated that she had no wish to become a model; she only used to model to support her acting career. She is still considered extremely hot compared to other Hollywood actresses, which is evident from the fact that she has appeared in several famous magazines as a model and has also campaigned for brands like Armani, Burberry, Dolce & Gabbana and Paul Smith.

She left modelling after some time to focus on acting. However, she said that she never intended to become an actress and in fact, she hates it. She somehow got involved in it since she got a good pay checkwhich was necessary to support her family. Her acting debut came in 1993 in the movie “Riders”, where she played a minor role as a horse rider. At the beginning of her acting career, she used to be a part time waitress, which she claims provided her lots of important experiences.

She acted in the movie “Principles of Lust” in 2003. One of the most famous scenes of that movie showed her gorgeous bare feet, while the actor was licking from her heels to her toes. Her breakthrough role came in 2004, when she played the role of Jill Valentine in the movie “Resident Evil: Apocalypse”, which was based on a video game of the same name. Owing to the success of the movie, she played several roles in films such as Eragon, Gunless etc. She resumed her role in the movie “Resident Evil: After life”, which released in 2010.

She has starred in several TV shows as well such as “Luther”, “CSI” etc. She is currently shooting for the upcoming TV series “Stan Lee's Lucky Man”.

Unlike popular celebrities of Hollywood, Sienna Guillory doesn’t have an extensive list of boyfriends. She started dating her first boyfriend, Nick Moran, an English actor and producer, in 1996. The two married in 1997. Unfortunately, their marriage didn’t last more than 4 years. They got divorced in 2000. She then began to date Enzo Cilenti that same year. Nick has starred in several famous Hollywood movies such as “Guardians Of The Galaxy”,“The Theory Of Everything”etc. They got married in 2002, and are now leading a happy and peaceful life. They also have two beautiful daughters.

Her estimated net worth is around $5 million as of this year.