In order to increase understanding of the structure and bonding of aromatic molecules and their fragments on transition metal surfaces, a low-energy electron diffraction (LEED) study of benzene adsorption on Ir{100} has been carried out. Following benzene adsorption at 465 K, a c(2x4) LEED pattern is observed. Its formation is accompanied by the loss of two hydrogen atoms as H-2, indicating that benzyne (C6H4) is formed. This is the first time an ordered overlayer of benzyne has been observed on a transition metal surface. It makes the structure accessible to LEED I-V analysis, providing the most reliable structural information for benzyne adsorbed on a transition metal surface to date. The benzyne species was found to be di-sigma bonded to the bridge site with a 47 degrees tilt angle to the surface normal.