Dreams are sometimes described as an intensified form of spontaneous waking thought. Lucid dreams may seem to be a counterexample, because metacognitive insight into the fact that one is now dreaming is often associated with the ability to deliberately control the ongoing dream. This chapter uses conceptual considerations and empirical research findings to argue that lucid dreaming is in fact a promising and rich target for the future investigation of spontaneous thought. In particular, the investigation of dream lucidity can shed light on the relationship between metacognitive insight and control, on the one hand, and the spontaneous, largely imagistic cognitive processes that underlie the formation of dream imagery, on the other hand. In some cases, even lucid insight itself can be described as the outcome of spontaneous processes, rather than as resulting from conscious and deliberate reasoning. This raises new questions about the relationship between metacognitive awareness and spontaneous thought.