Dipotassium cyclooctatetraenide, sometimes abbreviated K2COT, is an organopotassium compound with the formula K2C8H8.

It is a brown solid that is used as a precursor to cyclooctatetraenide complexes, such as uranocene (U(C8H8)2).

Analogs of K2C8H8 are known with ring substituents, with different alkali metals, and with various complexants.

Potassium cyclooctatetraenide is formed by the reaction of cyclooctatetraene with potassium metal: The reaction entails 2-electron reduction of the polyene and is accompanied by a color change from colorless to brown.

The C8H8 unit is planar with an average C-C distance of 1.40 A.