Copper arsenate (Cu3(AsO4)2·4H2O, or Cu5H2(AsO4)4·2H2O), also called copper orthoarsenate, tricopper arsenate, cupric arsenate, or tricopper orthoarsenate, is a blue or bluish-green powder insoluble in water and alcohol and soluble in aqueous ammonium and dilute acids.

Copper arsenate is an insecticide used in agriculture.

Anhydrous copper arsenate, Cu3(AsO4)2, is found in nature as the mineral lammerite.

[3] Copper arsenate tetrahydrate, Cu3(AsO4)2·4H2O, occurs naturally as the mineral rollandite.

[4] Copper arsenate hydroxide or basic copper arsenate (Cu(OH)AsO4) is a basic variant with CAS number 16102-92-4.