Melanie Jayne Lynskey ( LIN-ski; born 16 May 1977) is a New Zealand actress. Known for her portrayals of complex women and her command of American dialects, she works predominantly in independent films. Lynskey is the recipient of two Critics' Choice Awards, a HCA Award, a Gracie, a New Zealand Film Award, a Hollywood Film Award, and a Sundance Special Jury Award, as well as Gotham, Satellite, Saturn, Golden Nymph, Independent Spirit, Screen Actors Guild, and Primetime Emmy Award nominations.

Lynskey made her screen debut in Heavenly Creatures (1994), earning a New Zealand Film Award for her portrayal of teenage murderess Pauline Parker. She later appeared in various international productions, including Ever After (1998), Detroit Rock City, But I'm a Cheerleader, The Cherry Orchard (all 1999), Coyote Ugly (2000), Snakeskin (2001), Shooters, Abandon, and Sweet Home Alabama (all 2002). After moving to the United States, Lynskey became known as a character actor, gaining recognition for a mix of big-budget and small-scale film projects, such as Shattered Glass (2003), Flags of Our Fathers (2006), Away We Go, Up in the Air, The Informant!, Leaves of Grass (all 2009), Win Win (2011), Seeking a Friend for the End of the World, The Perks of Being a Wallflower (both 2012), They Came Together (2014), and Don't Look Up (2021).

In 2012, Lynskey received critical acclaim and a Gotham Award nomination for her starring role as a depressed divorcee in Hello I Must Be Going, which proved to be a turning point in her career. Subsequent lead parts in The Big Ask (2013), Happy Christmas, We'll Never Have Paris, Goodbye to All That (all 2014), The Intervention, Rainbow Time, Little Boxes (all 2016), I Don't Feel at Home in This World Anymore, And Then I Go (both 2017), Sadie (2018), and Lady of the Manor (2021) established her as a prominent figure in the American independent film community.Outside of film, Lynskey achieved fame with her portrayal of Rose on the CBS sitcom Two and a Half Men (2003–2015), and earned a Critics' Choice nomination for playing Michelle Pierson on the HBO series Togetherness (2015–2016). She provided the voices of Beatrice for Cartoon Network's Over the Garden Wall (2014) and Megan for Disney XD's Future-Worm! (2016–2018). After starring as Molly Strand on the first season of Hulu's Castle Rock in 2018, Lynskey appeared as Rosemary Thomson in the FX miniseries Mrs. America (2020), and as Betty Gore in the Hulu miniseries Candy (2022), receiving a nomination for the 2023 Critics' Choice Award for Best Supporting Actress for the latter. In 2021, she debuted in the lead role of Shauna on Showtime's Yellowjackets, for which she won the 2022 Critics' Choice Award for Best Actress in a Drama Series and was nominated for the 2022 Primetime Emmy Award for Outstanding Lead Actress. Lynskey is married to actor Jason Ritter, with whom she has a daughter.