: This chapter reviews the chemistry and application technology of fluorescent dyes as applied to textiles. Following a brief review of the historical background, the physical principles underlying fluorescence are presented. The molecular structures of fluorescent dyes for textile applications are illustrated and discussed in terms of general structural features and the most important chemical classes. Textile applications of fluorescence, using dyes and daylight fluorescent pigments, are reviewed together with a brief overview of some important non-textile applications of fluorescent dyes. The chapter concludes with informed speculation on likely future trends in fluorescence on textiles.