Phycoerythrocyanin is a tetrapyrrole blue molecule involved in photosynthesis, notably in Cyanobacteria and red algae. This chromophore is bound to the phycobiliprotein phycocyanin, an important component of the light-harvesting system of cyanobacteria and red algae (phycobilisome).

When bound to phycocyanin, phycoerythrocyanin leads to an absorption maximum around 620 nm. As it is the typical terminal acceptor chromophore of phycocyanin, it gives to this phycobiliprotein its characteristic fluorescence emission around 650 nm.