In this paper I am concerned with two questions: What is sexist humor? and what is wrong with it? To answer the first question, I briefly develop a theory of humor and then characterize sexist humor as humor in which sexist beliefs (attitudes/norms) are presupposed and are necessary to the fun. Concerning the second question, I criticize a common sort of argument that is supposed to explain why sexist humor is offensive: although the argument explains why sexist humor feels offensive, it does not place responsibility for the offense in the humorist or audience that enjoys sexist humor. I develop an alternate account of the offense in sexist humor that places responsibility for offense in precisely those quarters.