Cog may refer to:

• A part of a gear system
• Cog (ship), a small sailing vessel
• A tenon that extends all the way through another piece of wood, in joinery
• The evil robots in Toontown Online
• The evil robot drones of the Machine Empire seen in Power Rangers: Zeo
• The humanoid robot at the center of the MIT Cog project
• The Mount Washington Cog Railway
• Cog (television commercial), a Honda television commercial
• Cog (band), an Australian band
• Cog (Pinoy rock band), a Filipino rock band
• The programming language used in the Star Wars Jedi Knight: Dark Forces II and Star Wars Jedi Knight: Mysteries of the Sith video games
• A human soldier from the video game Gears of War
• Cog, an audio player for Mac OS X

COG is an acronym for:

• Canberra Ornithologists Group
• City of Genoa schools
• CANDU Owner's Group
• Center of gravity
• Central of Georgia Railroad
• Changing of the Guard, also known as Guard Mounting
• Children of God
• Children's Oncology Group
• Chip-on-glass (electronics)
• Church of God
• Clusters of Orthologous Groups of proteins
• Coalition of Ordered Governments (Gears of War)
• Consolidated Operations Group, Inc.
• Coke Oven Gas
• Concours Owners Group, a United States-based motorcycling club for riders of the Kawasaki Concours
• Continuity of government plans
• Cost of goods
• Council of Governments
• Course over Ground
• Covenant of the Goddess
• The Church of Google
• The ISO 3-letter country code of the Republic of the Congo
• Conserved Oligomeric Golgi complex
• Codemasters Online Gaming, the account service for Massively multiplayer online games (MMO) provided by Codemasters
• C0G (C zero G), another name for the NP0 temperature stable capacitor dielectric material
• Creepy old guy (phone texting shorthand)

See also

• COGS (dab)