It’s no secret that anarchists don’t like states. In fact, we anarchists are generally defined by our rejection of, and opposition to state institutions, such as governments, police, and prisons. But while opposing these physical manifestations of the state is certainly an important part of anarchist practice, anarchist critiques of the state go much further, and include the underlying social relationships and ideologies that have historically been used to create states, and to uphold their authority. One of the most important of these concepts is nationalism. So what is it, exactly, and what do anarchists have against it?