Fishtronaut (Portuguese: Peixonauta) is a Brazilian animated children's television series created by Célia Catunda and Kiko Mistrorigo, and produced by TV PinGuim, in association with Discovery Kids. The series is about the eponymous character, a fish in a spacesuit which allows him to fly and breathe out of water. He is a secret agent who, along with his friends Marina and Zeek, unravels the mysteries occurring in the Smiling Trees Park. They solve the mysteries with the help of a P.O.P. (Primary Objective Pod), a magical multicolored ball containing clues vital to the mission. Viewers are invited to dance along with the heroes to a tune, so that the P.O.P. will open and release the clues inside. The series is aimed at children ages 3–7 and debuted successfully on Discovery Kids in Latin America on 20 April 2009.

In the international market, the series is marketed by the names of Peztronauta (Spanish) or Fishtronaut (English). After success on TV, Fishtronaut was produced as a play called Peixonauta da TV para o Teatro (in English: Fishtronaut from TV to Theatre) which premiered on 9 January 2011 in Rio de Janeiro. On 9 November 2012, a movie titled Peixonauta – Agente Secreto da O.S.T.R.A. (in English: Fishtronaut – Secret Agent of O.Y.S.T.E.R.) was released. From 30 March 2015 to 25 December 2020, the series also aired on the now-defunct Qubo network, owned by Ion Media Networks.

The show has been noted for its success in teaching kids to care for the environment.