Lake Siegel Bell (born March 24, 1979) is an American actress, screenwriter and director. She has starred in various television series, including Boston Legal (2004–2006), Surface (2005–2006), How to Make It in America (2010–2011), Childrens Hospital (2008–2016), and Bless This Mess (2019–2020) and in films including Over Her Dead Body (2008), What Happens in Vegas (2008), It’s Complicated (2009), No Strings Attached (2011), Million Dollar Arm (2014), No Escape (2015), Man Up (2015), The Secret Life of Pets (2016), Shot Caller (2017) and Home Again (2017).
She wrote and directed the short film Worst Enemy, which debuted at the Sundance Film Festival in 2012, followed by her 2013 feature film directing debut In a World…, in which she also starred. In 2017, she directed, wrote, co-produced and starred in I Do… Until I Don’t. As of 2021, Bell starred as the voice of Poison Ivy in the HBO Max series Harley Quinn (2019–present), and Natasha Romanoff / Black Widow in the Disney+ series What If…? (2021).