The carbon suboxide anion C3O2− is generated in solid neon matrix. It is characterized by infrared absorption spectroscopy as well as quantum chemical calculations to have a planar Cs structure where two CO groups with significantly different bond lengths and angles are attached in a zigzag fashion to the central carbon atom. Bonding analysis indicates that it is best described by the bonding interactions between a neutral CO in a triplet excited state and a doublet excited state of CCO−.