The structure-selective precise synthesis of carbon nanotubes (CNTs) has been long sought in materials science. The aromatic molecules corresponding to segment structures of CNTs, i.e. carbon nanobelts (CNBs), have been of interest as templates for CNT growth. Although two of three types, armchair and chiral CNBs, have been synthesized recently, zigzag CNBs remain elusive. Herein we report the synthesis and isolation of a zigzag CNB. The synthesis involves an iterative Diels–Alder reaction sequence followed by reductive aromatization of oxygen-bridged moieties. As predicted by theoretical calculations, this CNB was isolated as a stable compound. The structure of the zigzag CNB was fully characterized by X-ray crystallography, and its wide energy gap with blue fluorescence properties were revealed by photophysical measurement. With synthetic strategies towards all three types of CNBs in hand, the road to the precise synthesis of CNTs can now proceed to the next stage.