Melanie Jayne Lynskey (/ˈlɪnski/ LIN-skee; born 16 May 1977) is a New Zealand actress. Known for her portrayals of complex women and her command of American accents, she works predominantly in independent films and television. She is the recipient of numerous accolades, including three Critics' Choice Awards and nominations for three Primetime Emmy Awards.

Lynskey made her film debut at age 17 portraying Pauline Parker in Heavenly Creatures (1994). She went on to establish herself as a character actress through supporting parts in Ever After (1998); But I'm a Cheerleader (1999); Coyote Ugly (2000); Sweet Home Alabama (2002); Shattered Glass (2003); Flags of Our Fathers (2006); Away We Go; Up in the Air; The Informant! (all 2009); Win Win (2011); The Perks of Being a Wallflower (2012); and Don't Look Up (2021). Her starring role in Hello I Must Be Going (2012) proved to be a turning point in Lynskey's career, with subsequent lead parts in Happy Christmas (2014), The Intervention (2016), and I Don't Feel at Home in This World Anymore (2017) highlighting her as a prominent figure in independent cinema.

On television, Lynskey played the recurring role of Rose on Two and a Half Men (2003–2015). Her other credits include Togetherness (2015–2016) and Castle Rock (2018), as well as the miniseries Mrs. America (2020) and Candy (2022). Since 2021, she has starred as Shauna on Yellowjackets, winning the 2022 Critics' Choice Award for Best Actress and being nominated twice for the Primetime Emmy Award for Outstanding Lead Actress (2022; 2023). For her portrayal of Kathleen on the first season of The Last of Us (2023), Lynskey received another Emmy nomination.

Lynskey was born in New Plymouth, New Zealand, to Kay Barbara (née Mahoney), a real estate agent, and Tim Lynskey, an orthopaedic surgeon. She has Irish, English, and Scottish ancestry; her surname originates in Ireland. Lynskey played an active role in the raising of her siblings; she is the eldest of five children, and has three brothers and one sister. She was raised in the Baptist faith.

When she was six, Lynskey's family moved to England for one year before returning to New Zealand. She recalls moving "a lot" due to her father's profession: "My dad was a medical student when I was born, so he was studying and going to different universities. And then he was doing his residency, so I was always the new kid in school." She later attended New Plymouth Girls' High School, where she was involved in the drama department and school plays. She has spoken about being shy at school and finding comfort in acting: "It was so freeing, having someone give me the words to say and not being myself for a minute. It just felt like a weight was lifted off my shoulders." After graduating high school, Lynskey studied for a year and a half at Victoria University of Wellington, majoring in English literature, but dropped out to focus on her film career.

Lynskey's professional debut came at age 15 with a starring role in Heavenly Creatures, a psychological drama based on a 1950s murder case. Lynskey portrayed Pauline Parker, a schoolgirl who conspires to kill her mother. She auditioned for the role when a casting director visited her high school; prior to this, five hundred girls had been considered for the part, but "none were right". Fran Walsh, who co-wrote the screenplay, admired Lynskey's "quiet intensity" and said, "We knew immediately that she was right for the role". Lynskey turned 16 during the making of Heavenly Creatures and was 17 by the time of its release in 1994. Critics were effusive about the performances, especially those of Lynskey and her co-star, Kate Winslet. Roger Ebert complimented the film's director, Peter Jackson, on picking "the right two actresses", noting that "There is a way Lynskey has of looking up from beneath glowering eyebrows that lets you know her insides are churning", while Richard Corliss wrote in his review for Time:

The film's serendipitous stroke was to find Winslet and, especially, Lynskey, a first-time actress. They are perfect, fearless in embodying teenage hysteria. They declaim their lines with an intensity that approaches ecstasy, as if reading aloud from Wuthering Heights. The giggles that punctuate the girls' early friendship are not beneath Winslet and Lynskey. The screams that end the film are not beyond them.

Heavenly Creatures is recognised as a milestone in New Zealand cinema. It was nominated for the Academy Award for Best Original Screenplay, while Lynskey was named Best Actress at the 1995 New Zealand Film Awards. She regards working with Jackson and Winslet as an important learning experience. She grew particularly close to Winslet during filming, who later told The Irish Times, "Mel is like the left side of my body. [We] had the exact relationship in terms of communication and love that Pauline and Juliet had. From the minute we saw each other." Despite the film's success, its creators tried to discourage Lynskey from pursuing a full-time acting career, as it was not thought to be realistic. She later revealed, "[People were] looking out for me [...] 'Thanks for doing this movie for us, and now be sure that you go to university and get a normal job.' No one wanted to be responsible for me being like, 'I'm gonna run off to Hollywood!' [...] New Zealanders are very practical. Everybody was kind of like, 'That was fun [but] it's not what your life is gonna be.'"