Lourd was born July 17, 1992, in Los Angeles, California, the only child of actress Carrie Fisher and talent agent Bryan Lourd. Lourd is the granddaughter of actress Debbie Reynolds and singer Eddie Fisher, and the niece of Todd Fisher, Joely Fisher, and Tricia Leigh Fisher, all of whom have worked in show business. She has a sister, Ava, from her father's marriage to Bruce Bozzi, who her father legally adopted.From her mother's side, she is of Russian Jewish and Scots-Irish descent. Her godmother is actress Meryl Streep. Writer Bruce Wagner is Lourd's godfather.
Lourd studied psychology at New York University, graduating in 2014. Lourd played the role of Lieutenant Connix in the new Star Wars trilogy sequel films "The Force Awakens" and "The Last Jedi". In 2015, Lourd was cast in the Fox horror-comedy series Scream Queens, co-starring Emma Roberts. She had a role in the American biographical crime-drama film Billionaire Boys Club, once again alongside Emma Roberts. Lourd played the enigmatic Gigi in Booksmart, a high school comedy film directed by Olivia Wilde and released in 2019.
- The seventh season of American Horror Story is the second time that Lourd has appeared in a Ryan Murphy series and the third time she will star alongside Emma Roberts.
- She is one of the five members of the AHS Repertory Company to be credited in the main cast in every season she appeared in.
- She is one of the seven actors to work on both American Horror Story and Scream Queens. The others are Cathy Marks, Colton Haynes, Dalton E. Gray, Emma Roberts, Riley Schmidt, and Skyler Samuels.
- In both Scream Queens and American Horror Story, Billie Lourd wears accessories or a hairstyle that pay homage to her mother, Carrie Fisher, primarily buns or braids meant to be reminiscent of the hairstyles worn by Fisher as Princess Leia.