Rosanilin is a hydrochloride that is the monohydrochloride of 4-[(4-aminophenyl)(4-iminocyclohexa-2,5-dien-1-ylidene)methyl]-2-methylaniline. One of the major constituents of Basic fuchsin, together with pararosanilin, magenta II and new fuchsin. It has a role as a carcinogenic agent, a fluorochrome and a histological dye. It contains a rosanilin(1+).