Mary Elizabeth Chieffo is an American actress known for portraying the Klingon L'Rell on the television series Star Trek: Discovery. Chieffo was born and grew up in the neighborhood of Valley Village, Los Angeles in California, only daughter of actors Michael Chieffo and Beth Grant.

Her acting debut was at the age of three when she played a sleeping girl in Sandra Bullock's short film Making Sandwiches, in which her mother also had a role, and later acted in various TV shows and short and feature films. As a child, she attended Shakespeare theater camp at the Theatricum Botanicum, where she performed in a variety of shows including Antony and Cleopatra. She attended the Drama division of Juilliard School in New York City, earning a Bachelor of Fine Arts degree in 2015.