Nell Theobald (c. 1945, Atlanta, Georgia – August 20, 1977, New York City, New York) was an American model and actress. She initially gained fame for being attacked by a lion during a BMW photo shoot at the International Automobile Show at the New York Coliseum in April 1966. The incident received international press coverage.
She later drew notoriety for obsessively stalking opera singer Birgit Nilsson for nine years; beginning at the summer of 1968 at the Bayreuth Festival and ending upon Theobald's suicide in 1977. Nilsson recounted her experiences with Theobald at length in her memoir La Nilsson which was published in 2005, and the stalking incident was featured in Opera News magazine and The New York Times.
As an actress she appeared on the New York stage, in television commercials, and made some minor appearances in films and television shows. She committed suicide on August 20, 1977, in New York City.
- Ralph Blumenthal (May 21, 2006). "Soprano's Tale: Obsession, Love and Death. Offstage". The New York Times. Retrieved August 6, 2009.
- Kathryn Leigh Scott (August 2009). "The Star and the Stalker". Opera News 74 (2). Retrieved August 6, 2009.