TMSS may refer to:
Two-Micron Sky Survey, an infrared astronomical survey and catalog Taiwanese Modern Spelling System, the basis for the Modern Literal Taiwanese orthography Trademark Security System, a copyright protection mechanism used by Sega that was subject of the 1992 Sega v. Accolade court case Thengamara Mohila Sabuj Sangha, third largest non-governmental organisation (NGO) in Bangladesh