In organic chemistry, nitroso refers to a functional group in which the nitric oxide () group is attached to an organic moiety. As such, various nitroso groups can be categorized as C-nitroso compounds (e.g., nitrosoalkanes; ), S-nitroso compounds (nitrosothiols; ), N-nitroso compounds (e.g., nitrosamines, ), and O-nitroso compounds (alkyl nitrites; ).