What are mental states? When we talk about people's beliefs or desires, are we talking about what is happening inside their heads? If so, might cognitive science show that we are wrong? Might it turn out that mental states do not exist? Mental fictionalism offers a new approach to these longstanding questions about the mind. Its core idea is that mental states are useful fictions. When we talk about mental states, we are not formulating hypotheses about people's inner machinery. Instead, we simply talk "as if" people had certain inner states, such as beliefs or desires, in order to make sense of their behaviour. This is the first book dedicated to exploring mental fictionalism. Featuring contributions from established authors as well as up-and-coming scholars in this burgeoning field, the book reveals the exciting potential of a fictionalist approach to the mind, as well as the challenges it faces. In doing so, it offers a fresh perspective on foundational debates in the philosophy of mind, such as the nature of mental states and folk psychology, as well as hot topics in the field, such as embodied cognition and mental representation. Mental Fictionalism: Philosophical Explorations is essential reading for advanced undergraduates, postgraduates and professionals alike.