Elizabeth Chase Olsen was born on February 16, 1989, in Sherman Oaks, California. Her mother, Jarnie, is a former dancer, while her father, Dave, is a real estate agent. She is the younger sister of twins Mary-Kate and Ashley Olsen, who became television and film actresses as children. Olsen also has an older brother, a younger half-brother, and a younger half-sister. Her parents divorced in 1996.
Olsen began acting when she was four years old, appearing in Mary-Kate and Ashley's projects, including the 1994 television film How the West Was Fun and the straight-to-video series The Adventures of Mary-Kate & Ashley.
Olsen made her film debut in the 2011 thriller film Martha Marcy May Marlene. Olsen earned several award nominations for her portrayal of the titular Martha, a young woman suffering from delusions after fleeing her life in a cult and returning to her family, including those for the Critics' Choice Movie Award for Best Actress and the Independent Spirit Award for Best Female Lead.
Olsen starred in the 2015 superhero film Avengers: Age of Ultron, a sequel to The Avengers, joining the Marvel Cinematic Universe media franchise and rising to fame. In the film, she portrayed Wanda Maximoff / Scarlet Witch, which marked the comic book character's film debut. Olsen played the part with an accent originating from a fictional country called Sokovia, which she described as similar to Slovakian. She reprised the role in Captain America: Civil War (2016), Avengers: Infinity War (2018), and Avengers: Endgame (2019), the lattermost of which became the second highest-grossing film of all time.
Olsen has been an atheist since the age of 13 because she believed that "religion should be about community and having a place to go in prayer, not something that should determine women's freedoms." She is an ambassador for the company Bobbi Brown Cosmetics. She and actor Boyd Holbrook were in a relationship from 2011 to 2014. Olsen became engaged to musician Robbie Arnett of the American band Milo Greene in July 2019 after three years of dating. She and Arnett live in Los Angeles. Olsen revealed in June 2021 that the two had married