• "Fido" is a common name for a pet dog, from the Latin fidelis, faithful.
• Fido (band), a punk/rock band from Melbourne, Australia
• Fido (film), a 2006 Canadian zombie comedy film
• Fido (software), a software scheduled media downloader for GNU/Linux
• fido.net, an internet service provider
• Fido Solutions, a Canadian cellular carrier owned by Rogers Wireless
• "Fido" is a common nickname for the Zimbabwean computer programming activist Fidelis Gwokuda
• Fido intelligence (A.I. designer team). Polish Natural Language Processing Research and Developmen Team
• Fido from the reggaeton duo Alexis & Fido

Fido may also refer to:

• Mark 24 FIDO Torpedo or Mark XXIV mine, a US acoustic homing torpedo used during the Second World War
• FidoNet is a non-commercial computer network founded by Tom Jennings
• FidoBBS, formally called FIDO, the name of the BBS software developed by Tom Jennings
• Claude (Grand Theft Auto), nicknamed Fido, from the computer and video game Grand Theft Auto III
• Fido Dido is a cartoon character associated with 7 Up soft drink
• Fido Explosives Detector is a portable explosives detector used extensively by the military for IED detection and people for explosives residue

FIDO is an acronym for:

• Flight Dynamics Officer, for whom FIDO is the NASA Mission Control call sign
• Fog Investigation and Dispersal Operation (FIDO), a fog dispersal system developed in the second world war
• Fire Direction Officer, commands the Fire Direction Center (FDC) for an artillery battalion.

fido is an acronym for

• flexible input, deterministic output, a microcontroller architecture of Innovasic, Inc