CYC or Cyc may refer to:

• Cycle gene (cyc) a circadian control gene found in  Drosophila melanogaster responsible for the formation of the formation of CYC protein.
• Cyc, an American artificial-intelligence project
• Champions Youth Cup (CYC), an annual international youth football (soccer) tournament
• China Youth Corps (CYC), a Taiwanese youth organization
• Cyclorama (theater) (Cyc), a curved fabric or plastic sheet backdrop for a stage
• Cycnoches (Cyc), a genus of orchid
• Cytochrome c, a protein of the mitochondrial electron transport chain.
• Cyclophosphamide, an anti-neoplastic and immunosuppressant drug.

Cyc is an artificial intelligence project that attempts to assemble a comprehensive ontology and knowledge base of everyday common sense knowledge, with the goal of enabling AI applications to perform human-like reasoning.