Dagmara Domińczyk (/doʊˈmiːntʃɪk/ doh-MEEN-chick, Polish: [daɡˈmara dɔˈmij̃t͡ʂɨk]; born 17 July 1976) is a Polish actress. She has appeared in the films Rock Star (2001), The Count of Monte Cristo (2002), Kinsey (2004), Trust the Man (2005), Lonely Hearts (2006), Running with Scissors (2006), Higher Ground (2011), The Letter (2012), The Immigrant (2013), Big Stone Gap (2014), A Woman, a Part (2016), The Assistant (2019), The Lost Daughter (2021), Bottoms (2023), and Priscilla (2023). Domińczyk also had a main role in the HBO comedy-drama television series Succession (2018–2023).

In 2013, she released her novel The Lullaby of Polish Girls.

Domińczyk was born in Kielce, the daughter of Aleksandra and Mirosław Domińczyk, a member of the Polish Solidarity movement. She moved with her family to New York City in 1983 as asylum seekers due to her parents' political associations (her father's involvement with Amnesty International and the Solidarity movement). She is the older sister of actresses Marika Domińczyk and Veronika Domińczyk.

Domińczyk was educated at Fiorello H. LaGuardia High School in Manhattan. She went on to study at Carnegie Mellon University's School of Drama in Pittsburgh, from which she graduated in 1998.

In 1999, Domińczyk made her acting debut on Broadway as Anna Friel's understudy in Patrick Marber's production of Closer. The following year, she made her feature film debut as Claire in the Stuart Blumberg-penned romantic comedy Keeping the Faith. In 2001, she played Tania Asher in Rock Star, and in 2002, portrayed Edmond Dantès' fiancée, Mercédès Mondego (née Herrera), in the screen adaptation of The Count of Monte Cristo.

In 2003, she returned to Broadway playing Caroline Bramble in a production of Enchanted April. Domińczyk had guest starring roles in television series such as Kinsey (2004), 24 (2005), The Bedford Diaries (2006), The Good Wife (2011), Suits (2011), Person of Interest (2012), and Boardwalk Empire (2014). In 2006, she appeared in the Todd Robinson–directed Lonely Hearts and the black comedy film Running with Scissors.

In 2011, Domińczyk co-starred in Vera Farmiga's directorial debut drama film Higher Ground as a religious group member who develops a brain tumor. The following year, she appeared in the psychological thriller film The Letter. She next appeared in James Gray's drama film The Immigrant (2013).

In 2013, she published her first novel, The Lullaby of Polish Girls, which was loosely based on her youth in her native Poland.