A horse opera, hoss opera, oat opera or oater is a Western film or television series that is clichéd or formulaic, in the manner of a (later) soap opera or space opera.^[1]

The term, which was originally coined by silent film-era Western star William S. Hart, is used variously to convey either disparagement or affection. The term "horse opera" is quite loosely defined; it does not specify a distinct sub-genre of the Western (as "space opera" does with regard to the science fiction genre).