校園霸凌對學生身心的影響既長且深遠，因而受到世界各國的重視。霸凌是一個團體動力的歷程，事件發生時大都有旁觀者在場，旁觀者是否採取行動以及採取何種行動，影響霸凌行為的持續或終止，因此，旁觀者在霸凌事件中扮演著關鍵性角色。本文旨在回顧霸凌旁觀者的重要文獻，首先釐清霸凌的意義，再依序介紹霸凌旁觀者行為的類型、相關理論、效果及影響因素，以及反霸凌方案實例等，期能喚起社會各方對於霸凌旁觀者角色的重視，進而有助於校園「零霸凌」目標的達成。

School bullying has become one of the most important educational issues worldwide because it could cause students' mental and psychosocial problems and have long-term impacts on their future lives. Bullying is a dynamic process in which bystanders play critically important role in determining or continuing a bullying event. The purpose of this paper was to review the literature on bullying bystanders, including the definitions of bullying, types of bullying bystander behavior, theoretical bases of bullying bystander, causes and effects of bullying bystander behavior, and two of the anti-bullying programs.