Myrtillin is an anthocyanin. It is the 3-glucoside of delphinidin. It can be found in plants, most abundantly in black beans, blackcurrant, blueberry, huckleberry, bilberry leaves and in various myrtles, roselle plants, and Centella asiatica plant.^{[citation needed]} It is also present in yeast and oatmeal.^{[citation needed]} The sumac fruit's pericarp owes its dark red colour to anthocyanin pigments, of which chrysanthemin, myrtillin and delphinidin have been identified.^{[unreliable source?]}

The various colors, such as red, mauve, purple, violet, and blue in Hydrangea macrophylla are developed from myrtillin complexes with metal ions called metalloanthocyanins.

Anthocyanidin 3-O-glucosyltransferase converts delphinidin to myrtillin in plants including Silene dioica and Vitis vinifera. The glucose unit is transferred from UDP-glucose, giving uridine diphosphate (UDP) as a byproduct.

The enzyme anthocyanin 3-O-glucoside 6''-O-hydroxycinnamoyltransferase from Perilla frutescens produces delphinidin 3-(6-p-coumaroyl)glucoside from myrtillin and p-coumaroyl-CoA in the anthocyanin biosynthesis pathway.