Cynthia Ellen Nixon (born April 9, 1966) is an American actress, activist, and theater director. For her portrayal of Miranda Hobbes in the HBO series Sex and the City (1998–2004), she won the 2004 Primetime Emmy Award for Outstanding Supporting Actress in a Comedy Series. She reprised the role in the films Sex and the City (2008) and Sex and the City 2 (2010), as well as the television show And Just Like That... (2021–present). Her other film credits include Amadeus (1984), James White (2015), and playing Emily Dickinson in A Quiet Passion (2016).

Nixon made her Broadway debut in the 1980 revival of The Philadelphia Story. Her other Broadway credits include The Real Thing (1983), Hurlyburly (1983), Indiscretions (1995), The Women (2001), and Wit (2012). She won the 2006 Tony Award for Best Actress in a Play for Rabbit Hole, the 2008 Primetime Emmy Award for Outstanding Guest Actress in a Drama Series for Law & Order: Special Victims Unit, the 2009 Grammy Award for Best Spoken Word Album for An Inconvenient Truth, and the 2017 Tony Award for Best Featured Actress in a Play for The Little Foxes. Her other television roles include playing political figures Eleanor Roosevelt , Kade Prenall in NBC Hannibal Warm Springs (2005), Michele Davis in Too Big to Fail (2011), and playing Nancy Reagan in the 2016 television film Killing Reagan. In 2020, she appeared in the Netflix drama Ratched.