Past and current major biological control programmes against defoliating insects in Eucalyptus plantation forest systems are reviewed. While some defoliating Australian lepidoptera, including a number of leafrollers, have invaded overseas plantations, classical biocontrol has been undertaken only against Uraba lugens (gum leaf skeletoniser), for which a larval endoparasitoid Cotesia urabae has been introduced into New Zealand. The most serious invasive Eucalyptus defoliators around the world, that require classical biological control to manage their impacts, have been the closely related weevils Gonipterus platensis, Gonipterus pulverulentus, Gonipterus sp. 2, and the paropsine beetles Paropsis charybdis, Trachymela sloanei and Trachymela tincticollis. One other classical biocontrol programme has been successful against a relatively minor pest, a sawfly Phylacteophaga froggatti, in New Zealand. The most common type of enemy introduced for control of defoliating pests has been egg parasitoids.