3-[N-(2-Carboxyethyl)methylamino]-7-[N-ethyl(3-sulfonatopropyl)amino]phenoxazin-5-ium (EVOblue 30) is a fluorescent dye for covalently labeling a wide range of biological molecules. The lower excitation energy needed for EVOblue 30 causes less photodestruction and exceeds the lifetime of the fluorescent signal compared to common dyes. EVOblue 30 is optimized for an excitation at 635 nm and an emission around 670 nm - both allowing the use of common laser and filter sets. In contrast to commercially available red excitable dyes, EVOblue 30 reveals a chemical stability and suitability for high performance fluorescence applications. It is a fluorescent marker for the red spectral region which is very stable and amine-reactive.