Julianne Nicholson (born July 1, 1971) is an American actress. She is best known for her roles in the films August: Osage County (2013) and Blonde (2022), as well as the television series Law & Order: Criminal Intent (2006–2009), Masters of Sex (2013–2014), Eyewitness (2016), and Mare of Easttown (2021), the lattermost of which earned her a Primetime Emmy Award.

Nicholson's other notable credits include Tully (2000), Ally McBeal (2001–2002), Kinsey (2004), Conviction (2006), Boardwalk Empire (2011–2013), Black Mass (2015), I, Tonya (2017), Togo (2019), and The Outsider (2020).