Cyclohexanethiolate-protected gold cluster Au-25(c-HT)(18) was isolated for the first time as a minor byproduct of [Au-23(c-HT)(16)](-). Single-crystal X-ray structure analysis revealed that Au-25(c-HT)(18) has an icosahedral Au-13 core, in sharp contrast to the face-centered cubic cores in major products such as [Au-23(c-HT)(16)](-) and Au-28(c-HT)(20). Au-25(c-HT)(18) prefers a neutral state to an anionic state, probably because the Au-13 core is forced to deform due to the steric hindrance between the c-HT ligands.