[6.8](3)Cyclacene as the first hydrocarbon being a fully conjugated molecular belt has been synthesized in an eight-step reaction sequence starting from 4,6-dimethylisophthalaldehyde. It is the smallest and most strained member of the [6.8] cyclacene family, and the synthetic path offers a general route to its higher members. The structural pattern of [6.8](3)cyclacene represents a model for a novel type of carbon nanotubes.