Marjorie Susan Monaghan (born March 19, 1964) is an American actress best known for her portrayal of Tessa Halloran (aka 'Number One') in the television series Babylon 5. Early life Monaghan was born March 19, 1964 in Orange County, California. She is of Irish-Celt ancestry and started acting in high school. Career Monaghan has performed in a number of science fiction television roles, including starring as "JoJo" in Space Rangers and an episode of Star Trek: Voyager. In 1999 she appeared in all eight episodes of Rescue 77 as a character named "Kathleen Ryan". Monaghan is best known for her appearances in 7 episodes Babylon 5 as a character named "Number One" (Tessa Holloran). Personal life Monaghan started dating Grant Rosenberg in 2001 whom she later married on February 2, 2011. Filmography Film Television References External links The Official Marjorie Monaghan Website 1964 births 20th-century American actresses 21st-century American actresses American film actresses American stage actresses American television actresses Actresses from Cincinnati Place of birth missing (living people) Living people