Planar hexacoordinate carbon in chemistry describes a molecular geometry featuring a planar arrangement of carbon with six surrounding atoms. No actual chemical compounds having this particular hexacoordinate configuration have been reported but quantum mechanical methods have demonstrated that these molecules are a possibility. Examples of molecules investigated with computational methods are the B<sub>6</sub>C dianion, the CN<sub>3</sub>Be<sub>3</sub><sup>+</sup> ion, the CO<sub>3</sub>Li<sub>3</sub><sup>+</sup> ion and the CN<sub>3</sub>Mg<sub>3</sub><sup>+</sup> ion. A simulated Be<sub>2</sub>C monolayer is reported to consist of quasi-planar hexacoordinate carbon atoms.
On the other hand, experimental research has confirmed that the pentagonal-pyramidal hexamethylbenzene ion, C<sub>6</sub>(CH<sub>3</sub>)<sub>6</sub><sup>2+</sup>, contains a hexacoordinate carbon atom. Furthermore, a heptacoordinate carbon atom has been predicted to be involved in a stable hexagonal-pyramidal configuration of tropylium trication, (C<sub>7</sub>H<sub>7</sub>)<sup>3+</sup>.