Upset may refer to:
Upset (band), an American rock band Upset (competition), where a likely winner loses "Upset" (Hit the Floor), an episode of the television series Hit the Floor Upset (horse), a racehorse Upset (wastewater treatment), temporarily decreased effluent quality Aircraft upset, a dangerous aviation condition Upper set, in mathematics UpSet Plot, in data visualization Upset forging, a forging process where a workpiece's diameter is increased by compressing its length. Upset, a type of fault in wood, see Shakes (timber) § Thunder shake or upset