Triafulvalene or cyclopropenylidenecyclopropene is a fulvalene hydrocarbon with chemical formula C<sub>6</sub>H<sub>4</sub>, composed of two linked cyclopropene rings. Triafulvalene has never been isolated, since it can decompose via an isodesmic reaction. However, its structure, stability, and spectral properties are well-studied theoretically; the molecule is believed planar.