After studying drama at the Royal Academy of Dramatic Art, Rigg joined the Royal Shakespeare Company in the days when Peter Hall was director. With senior actors like Edith Evans, Charles Laughton and Laurence Olivier still performing with the company, Rigg enjoyed an auspicious start to her highly distinguished stage career with her Helena in "A Midsummer Night's Dream" and as the demure Cordelia in "King Lear".
Rigg surprised many of her colleagues with her next career move, but for many fans, she is most affectionately remembered for her sleek, sexy, good-humored detective Emma Peel, frequently clad in black leather and ready to dispense with both karate chops or witty quips, on the cult TV adventure series, "The Avengers" (1965-69). "Diana" (NBC, 1973-74) was a mildly likable but less successful TV sitcom follow-up, but by then Rigg had ventured into occasional feature films. Most notable here were the satirical, Paddy Chayefsky-scripted black comedy of "The Hospital" (1971), the highly enjoyable horror send-up "Theater of Blood" (1973), and the Agatha Christie mystery "Evil Under the Sun" (1982).
Rigg's wide eyes, rich speaking voice and cool elegance stood her in good stead as middle age approached, her slightly sharp quality lending edge to her Broadway work in "The Misanthrope" (1974-75), her tour with a musicalized life of fin-de-siecle novelist and wit "Colette" (1982), and a memorable Tony-winning turn as the vengeful "Medea" (1994). Her intriguing combination of the passionate and the aloof also marked her US TV-movie debut as a woman who renounces both love and a career to become a cloistered nun in "In This House of Brede" (CBS, 1975). Her singing talent found occasional expression onstage, as in the London production of Stephen Sondheim's "Follies" (1987), and her sly but regal grace made her a welcome host (and sometimes actor) of the British-made PBS anthology series, "Mystery!", beginning in 1989 after Vincent Price left the program.
Rigg went on to appear in a host of television movies and miniseries as well as the occasional film and was nominated for an Emmy in 2002 for her portrayal of Baroness Lehzen in the critically acclaimed miniseries "Victoria & Albert."