Penny Hofstadter is a fictional character from the American CBS sitcom The Big Bang Theory, portrayed by actress Kaley Cuoco. She is the primary female character in the series, befriending her neighbors Leonard Hofstadter (Johnny Galecki) and Sheldon Cooper (Jim Parsons), two physicists employed at the California Institute of Technology (Caltech). Penny's lack of advanced education sets her apart from the group, and her outgoing personality and social aptitude drastically contrasts with the personalities of the primary male characters in the series. She is the primary love interest of Leonard, with whom she maintains a brief romantic relationship during the third season, which is later resumed in the fifth season and culminates in their engagement at the end of the seventh season and their wedding at the start of season nine.