Sadie Elizabeth Sink (born April 16, 2002) is an American actress. She began her acting career in theatre, playing the title role in the musical Annie (2012–14) and young Elizabeth II in the historical play The Audience (2015) on Broadway. In 2016, she made her film debut in the biographical sports drama Chuck.

Sink had her breakthrough portraying Max Mayfield in the Netflix science fiction series Stranger Things (2017–2025) and received critical acclaim for her performance in its fourth season. In 2021, she appeared in the horror film trilogy Fear Street and played the lead role in Taylor Swift's short film All Too Well. She then starred in Darren Aronofsky's psychological drama The Whale (2022), for which she received a Critics' Choice Movie Award nomination. Sink returned to Broadway in 2025, starring in the play John Proctor Is the Villain and earning a nomination for a Tony Award for Best Actress in a Play; the second youngest woman to achieve such.