(+)-Car-3-ene synthase (EC 4.2.3.107, 3-carene cyclase, 3-carene synthase, 3CAR, (+)-3-carene synthase) is an enzyme with systematic name geranyl-diphosphate diphosphate-lyase [cyclizing, (+)-car-3-ene-forming]. This enzyme catalyses the following chemical reaction
The enzyme reacts with (3S)- diphosphate twice as rapidly as geranyl diphosphate.