Molybdenum hexacarbonyl (also called molybdenum carbonyl) is the chemical compound with the formula Mo(CO)₆. This colorless solid, like its chromium and tungsten analogues, is noteworthy as a volatile, air-stable derivative of a metal in its zero oxidation state.

Mo(CO)₆ adopts an octahedral geometry consisting of six rod-like CO ligands radiating from the central Mo atom. A recurring minor debate in some chemical circles concerns the definition of an "organometallic" compound. Usually, organometallic indicates the presence of a metal directly bonded via a M–C bond to an organic fragment, which must in turn have a C–H bond. By this strict definition, Mo(CO)₆ is not organometallic.

Mo(CO)₆ is prepared by the reduction of molybdenum chlorides or oxides under a pressure of carbon monoxide, although it would be unusual to prepare this inexpensive compound in the laboratory. The compound is somewhat air-stable and sparingly soluble in nonpolar organic solvents.

Mo(CO)₆ has been detected in landfills and sewage plants, the reducing, anaerobic environment being conducive to formation of Mo(CO)₆.

Mo(CO)₆ is a popular reagent in organometallic synthesis because one or more CO ligands can be displaced by other donor ligands. Mo(CO)₆, [Mo(CO)₃(MeCN)₃], and related derivatives are employed as catalysts in organic synthesis for example, alkyne metathesis and the Pauson–Khand reaction.

Mo(CO)₆ reacts with 2,2′-bipyridine to afford Mo(CO)₄(bipy). UV-photolysis of a THF solution of Mo(CO)₆ gives Mo(CO)₅(THF).

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