Bertrandite is a beryllium sorosilicate hydroxide mineral with composition: Be4Si2O7(OH)2.

Bertrandite is a colorless to pale yellow orthorhombic mineral with a hardness of 6–7.

It is commonly found in beryllium rich pegmatites and is in part an alteration of beryl.

Associated minerals include beryl, phenakite, herderite, tourmaline, muscovite, fluorite and quartz.

It was discovered near Nantes, France in 1883 and named after French mineralogist, Emile Bertrand (1844–1909).