More study is needed to make VANETs more relevant. Opportunistic routing (OR) is a new model that has been proposed for wireless networks. OR has emerged from the research communities because of its ability to increase the performance of wireless networks. It benefits from the broadcast characteristic of wireless mediums to improve network performance. The basic function of OR is its ability to overhear the transmitted packet and to coordinate among relaying nodes. In this chapter, an exhaustive survey of existing OR protocols is done by considering various factors. More precisely, existing secure OR protocols are deliberated. Future directions of research are also included, which provide a superior way to overcome some of the limitations of these existing protocols. Through this detailed survey, an outline and in-depth knowledge of existing OR protocols can be acquired. © 2018, IGI Global.