Recent years have seen an explosion of interest in genes that function for their own good and to the detriment of other genes residing in the same genome. Such intragenomic conflicts are increasingly recognised to underpin maladaptation and disease. However, progress has been impeded by a lack of clear understanding as to what intragenomic conflict actually means, and an associated obscurity concerning its fundamental drivers. We develop a general theory of intragenomic conflict in which genes are viewed as inclusive-fitness-maximizing agents that come into conflict when their inclusive-fitness interests disagree. This yields a classification of all intragenomic conflicts into three categories according to whether genes disagree about where they have come from, where they are going, or where they currently are. We illustrate each of these three basic categories, survey and classify all known forms of intragenomic conflict, and discuss the implications for organismal maladaptation and human disease.