Philosophers have attempted to explain humour in various ways over the years. Drawing on the main philosophical theories of humour – the superiority theory, the relief theory, and the incongruity theory – along with the psychological theory of benign violation, I elucidate what makes swearing (sometimes) funny. I argue that each of these theories has something to contribute to understanding swearing's funniness and that, in addition, its funniness also likely derives from two other factors. One of these factors is the glee that many of us came to attach to uttering naughty words when we were children. The other factor is the emotion-intensifying unpredictability (‘Whatever will happen next?’) introduced by the breaking of norms that occurs when someone swears inappropriately, which – provided that the norm-breaking does not introduce a threat – provokes amusement.