Acting career

In 1969, Seymour appeared uncredited in her first film, Richard Attenborough's Oh! What a Lovely War. In 1970, Seymour appeared in her first major film role in the war drama The Only Way. She played Lillian Stein, a Jewish woman seeking shelter from Nazi persecution. In 1973, she gained her first major television role as Emma Callon in the successful 1970s series The Onedin Line. During this time, she appeared as female lead Prima in the two part television miniseries Frankenstein: The True Story. She appeared as Winston Churchill's girlfriend Pamela Plowden in Young Winston, produced by her father-in-law Richard Attenborough.

In 1973, Seymour achieved international fame in her role as Bond girl Solitaire in the James Bond film Live and Let Die. IGN ranked her as 10th in a Top 10 Bond Babes list.^[17] In 1975, Seymour was cast as Princess Farah in Sinbad and the Eye of the Tiger, the third part of Ray Harryhausen's Sinbad trilogy. The film was not released until its stop motion animation sequences had been completed in 1977. In 1978, she appeared as Serina in the Battlestar Galactica film and in the first five episodes of the television series. Seymour returned to the big screen in the comedy Oh Heavenly Dog opposite Chevy Chase.

In 1980, Seymour played the role on stage of Constanze in Peter Shaffer's play Amadeus, opposite Ian McKellen as Salieri and Tim Curry as Mozart. The play premiered on Broadway in 1980, ran for 1,181 performances and was nominated for seven Tony Awards, of which it won five.

Also in 1980, Seymour was given the role of young theatre actress Elise McKenna in the period romance Somewhere in Time. Though the film was made with a markedly limited budget, the role enticed Seymour with a character she felt she knew. The effort was a decided break from her earlier work, and marked the start of her friendship with co-star Christopher Reeve.

In 1981, she appeared in the television film East of Eden, based on the novel by John Steinbeck. Her portrayal of main antagonist Cathy Ames won her a Golden Globe.^[18] In 1982, she appeared in The Scarlet Pimpernel with Anthony Andrews and her Amadeus costar Ian McKellen. In 1984, Seymour appeared nude in the film Lassiter, co-starring Tom Selleck, but the film was a box office flop. In 1987, Seymour was the subject of a pictorial in Playboy magazine, although she did not pose nude.

In 1988, Seymour got the female lead in the twelve part television miniseries War and Remembrance, the continued story from the miniseries The Winds of War. She played Natalie Henry, an American Jewish woman trapped in Europe during World War II. That same year, she won an Emmy Award for playing Maria Callas in the television movie Onassis: The Richest Man in the World.^[19][20]

In 1989, on the occasion of the 200th anniversary of the French Revolution, Seymour appeared in the television film La révolution française, filmed in both French and English. Seymour appeared as the doomed French queen, Marie Antoinette; Seymour's two children, Katherine and Sean, appeared as the queen's children.

In the 1990s, Seymour earned popular and critical praise for her role as Dr. Michaela "Mike" Quinn in the television series Dr. Quinn, Medicine Woman and its television sequels (1993–2001). Her work on the series earned her a second Golden Globe Award. While working on the series Dr. Quinn, Medicine Woman, she met her fourth husband, actor director James Keach.

In the 2000s, Seymour continued to work primarily in television. In 2004 and 2005, she made six guest appearances in The WB series Smallville, playing Genevieve Teague, the wealthy, scheming mother of Jason Teague (Jensen Ackles). In 2005, Seymour returned to the big screen in the comedy Wedding Crashers, playing Kathleen Cleary, wife of fictional United States Secretary of the Treasury William Cleary, played by Christopher Walken. In spring 2006, she appeared in the short lived The WB series Modern Men. Later that year, Seymour guest-starred as a law-school-professor on an episode of the CBS sitcom How I Met Your Mother and as a wealthy client on the Fox legal drama Justice. In 2007, she guest-starred in the ABC sitcom In Case of Emergency. She also appeared in ITV's Marple: Ordeal By Innocence, based on the Agatha Christie novel. She was a contestant on season five of the US reality show Dancing with the Stars; she finished in sixth place, along with her partner Tony Dovolani. Seymour guest starred in "One Life to Lose", a soap opera-themed episode of the ABC crime-dramedy Castle.

Seymour appeared in the Hallmark Channel film Dear Prudence (2008); the romantic comedy Love, Wedding, Marriage (2011); and the Hallmark Movie Channel film Lake Effects (2012).

In April 2016, she starred as Florence Lancaster in Noël Coward's play The Vortex, presented in Singapore by the British Theatre Playhouse.^[21] In 2022, Seymour became the leading character and executive producer in the Irish TV series Harry Wild.