Methylthionine chloride wani sinadari ne wanda kuma aka sani da methylene blue. Rini ne na asali mai launin shuɗi wanda ake amfani da shi a aikace-aikace daban-daban kamar lalata kyallen jikin halitta, a matsayin rini a cikin yadudduka, da kuma matsayin magani ga methemoglobinemia, yanayin da jini ba zai iya ɗaukar iskar oxygen yadda ya kamata. Hakanan za'a iya amfani da shi azaman mai nuna alamar redox a cikin sinadarai na nazari.