The Alexa Fluor family of fluorescent dyes is produced by Molecular Probes, Inc., a wholly owned subsidiary of Thermo Fisher Scientific. Alexa Fluor dyes are frequently used as cell and tissue labels in fluorescence microscopy and cell biology.

The excitation and emission spectra of the Alexa Fluor series cover the visible spectrum and extend into the infrared. The individual members of the family are numbered according roughly to their excitation maxima (in nm).