We report the challenging synthesis and electronic properties of a new class of rhombic peri-fused acene dimers, the so-called peri-acenoacenes. Compared to rectangular peri-fused peri-acenes, peri-acenoacenes show less diradical character and higher stability. Two soluble and stable aryl-substituted peri-acenoacenes, peri-tetracenotetracene (TT-Ar) and peri-pentacenopentacene (PP-Ar), are synthesized and their structures are confirmed by X-ray crystallographic analysis. Their optical properties and electronic properties are different from those of peri-acene derivatives. Unexpectedly, both the neutral compounds and dications are aromatic.