The flagellosperm of insects, although following a general ground plan, exhibit considerable variation in morphology and ultrastructure across taxa, consistent with a history of rapid and divergent evolution. Sperm competition, which occurs when sperm of two or more males compete for the fertilization of a female’s ova, has been recognized as a significant driving force in the evolution of insect sperm structure. Despite a considerable volume of data on sperm morphology, little is known about the motility of insect sperm. Understanding insect sperm motility would help to refine models of sexual selection on insect sperm, and would throw light on the selective mechanisms that shape insect sperm structure and function. This review updates our present knowledge of the proximate and ultimate aspects of insect sperm motility.