Fiver may be:
- A common slang term for:
- An Australian five-dollar note
- A British five-pound note
- A five-euro note
- A United States five-dollar bill
- A fifth columnist or saboteur, in wartime slang
- A large forehead, generally the height of five fingers placed horizontally on the forehead.
- Fiver (racing), a Swedish endurance racing team
- 5*, a UK TV channel operated by Channel 5 formerly known as Fiver
- Fiver (puzzle), a math game played on a 5x5 grid, distantly related to Conway's Game of Life
- Fiver (Watership Down), a fictional rabbit in the Richard Adams novel Watership Down
- The Fiver, a humorous daily football email by The Guardian newspaper
- Fiverr, a global online marketplace for buying and seling services starting at $5
- Zaidiyyah Shi'a Muslims, who disagree with the majority of Shi'a on the identity of the Fifth Imam