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).