益虫指进行对其他生物有益的活动的昆虫。界定益虫的标准相当主观：人类往往衡量某个品种的昆虫对人类的贡献多寡去判断其是否益虫。例如从农业的角度看，种植农作物是首要的目标，所以任何协助农作物生长的昆虫均被视为益虫。

一种昆虫可于一个领域里被视为害虫，而在另一个领域里成为益虫

在有机种植中，协助益虫繁衍（如提供较好的生存环境）是防治虫害的常用策略。有些从事虫害防治的公司有向农场或园圃出售益虫，尤其受拥有温室的农场欢迎。

Biological control is a bioeffector-method of controlling pests (including insects, mites, weeds and plant diseases) using other living organisms. It relies on predation, parasitism, herbivory, or other natural mechanisms, but typically also involves an active human management role. It can be an important component of integrated pest management (IPM) programs. There are three basic types of biological pest control strategies: importation (sometimes called classical biological control), augmentation and conservation.