Jeffrey Duncan Jones (born September 28, 1946) is an American actor known for his roles as Emperor Joseph II in Amadeus (1984), Edward R. Rooney in Ferris Bueller's Day Off (1986), Charles Deetz in Beetlejuice (1988), Dr. Skip Tyler in The Hunt for Red October (1990), Eddie Barzoon in The Devil's Advocate (1997), and A. W. Merrick in both Deadwood (2004–2006) and Deadwood: The Movie (2019).

His career started in Guthrie Theater in Minneapolis, and advanced to London and Broadway. In film and television, Jones has had many roles which capitalized on his deadpan portrayal of characters in unusual situations, often to comic effect. He was nominated for a Golden Globe Award for his performance in Amadeus and a Screen Actors Guild Award as part of the ensemble cast of Deadwood.

In 2002, Jones was charged with soliciting a minor to pose for nude photographs wearing a cowboy hat, dressed as an indigenous person, holding a stuffed animal. The offenses occurring in 1999 and 2000. In July 2003 he pleaded no contest and prosecutors dropped possession of child pornography charges. He was then sentenced to 5 years of probation, 1 year psychological counseling, and 2 years of drug and alcohol abuse counseling, Jones also was required to register as a sex offender for life and prohibited from possessing pornography, and later had two subsequent arrests for failing to update his sex offender status the first incident occurring one year later in July 2004 and the other in 2010, the following September he was sentenced to 250 hours of community service plus 3 years of probation.

Jones was born in Buffalo, New York, the son of Ruth (née Schooley) and Douglas Bennett Jones. His mother was an art historian, who urged him towards a career in acting. His father died when Jones was an infant.

After graduating from The Putney School in 1964, Jones enrolled in Lawrence University as a premed student, where his performances in university productions brought him to the attention of Tyrone Guthrie, who recruited him for the Guthrie Theater in Minneapolis, Minnesota.

His stage career included more than 125 productions, starting with the Guthrie Theater, then internationally in South America, Canada, and London, and in New York Off-Broadway in Cloud 9 and Henry V, among other productions, as well as on Broadway in productions including Trelawny of the "Wells" and The Elephant Man. His transition from stage to film began in 1970.

Jones began acting in small parts in film and television in the 1970s. In his best-known roles as Emperor Joseph II in Amadeus, Charles Deetz in Beetlejuice, and Edward R. Rooney in Ferris Bueller's Day Off, his dead-pan expression and distinctive face bring a comic flavor to his characters through their reactions to the situations in which they find themselves, more so than the wit in their scripted lines. The New York Times' biographic profile reads: "Although he has tried to steer clear of playing only sinister roles, the actor's imposing height, bugged-out eyes, easy sneer, and shock of reddish-blond hair give him vaguely devilish features that have prompted villain typecasting. However, the actor is also widely respected and considered a boon wherever he appears." The profile describes his portrayals variously as a "hissable, cartoonish high school principal" in Ferris Bueller's Day Off, a "good-natured father" in Beetlejuice, "an interplanetary freedom fighter" in Mom and Dad Save the World, a "demon stand-in" in Stay Tuned, and "evil bespectacled twins" in Out on a Limb.

Jones's work in the Lucille Lortel Theatre production of Cloud 9 was noticed by the casting team of Easy Money (1983), earning Jones a supporting role opposite Rodney Dangerfield.