Chromocene, formally known as bis(η⁵-cyclopentadienyl)chromium(II), is a chemical compound with the condensed structural formula [Cr(C₅H₅)₂]. Each molecule contains an atom of chromium bound between two planar systems of five carbon atoms known as cyclopentadienyl (Cp) rings in a sandwich arrangement, which is the reason its formula is often abbreviated as Cp₂Cr. It is an organometallic compound as it has (haptic) covalent chromium–carbon bonds. Chromocene is structurally similar to ferrocene, the prototype for the metallocene class of compounds; however, as it has only 16 valence electrons, it does not follow the 18-electron rule. It is a paramagnetic compound and also highly reducing, both consequences of its low valence electron count. Like structurally related metallocenes, chromocene readily sublimes in a vacuum and is soluble in non-polar organic solvents.

Ernst Otto Fischer, who shared the 1973 Nobel Prize in Chemistry for his work on sandwich compounds, was the first to report a synthesis for chromocene. One simple method of preparation involves the reaction of chromium(II) chloride with sodium cyclopentadienide:

Such syntheses are typically conducted in THF; decamethylchromocene, Cr[C₅(CH₃)₅]₂, can be prepared analogously from LiC₅(CH₃)₅. Chromocene can also be prepared from chromium(III) chloride in a redox process:

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