Philosophers have long been fascinated by the stream of consciousness – thoughts, images, and bits of inner speech that dance across the inner stage. Yet for centuries, such ‘mind‐wandering' was deemed private and thus resistant to empirical investigation. Recent developments in psychology and neuroscience have reinvigorated scientific interest in the stream of thought. Despite this flurry of progress, scientists have stressed that mind‐wandering research requires firmer philosophical foundations. The time is therefore ripe for the philosophy of mind‐wandering. Our review begins with a foundational question: What is mind‐wandering? We then investigate the significance of mind‐wandering for general philosophical topics, namely, mental action, introspection, and the norms of thinking and attention.