Mary Chieffo is an American actress best known for her role as L'Rell, a Klingon warrior and later Chancellor of the Klingon Empire, in Star Trek: Discovery. Born on November 7, 1992, in Los Angeles, California, she grew up in a family of actors—her parents are Michael Chieffo and Beth Grant. She pursued her passion for acting at the Juilliard School, earning a Bachelor of Fine Arts degree in 2015. Beyond Star Trek, Chieffo has been deeply involved in theater and immersive storytelling. She starred in and produced Operation Othello, a virtual reality adaptation of Shakespeare's Othello, where she played Lt. Iago in a gender-swapped version of the classic role. She later reprised this character in Iago: The Green-Eyed Monster, a futuristic musical AR prequel to Othello, which was nominated for Best Immersive Experience at the 2022 Tribeca Festival.

      Chieffo has also been vocal about queer representation in media. She publicly came out as panromantic demisexual and proudly in a lesbian relationship in 2021. She later confirmed she was dating writer and actor Madi Goff. In 2023, she wrote the introduction essay for Marvel's Voices: Pride #1, reflecting on the importance of LGBTQ+ visibility.

      Her career continues to evolve, with recent projects including a voice role in Star Trek: Lower Decks in 2024. She remains an advocate for diverse storytelling, blending her love for Shakespeare, sci-fi, and immersive media into her work.