The paradigm case of self-defense is defense against a culpable aggressor. However, there are also other cases discussed under the heading of self-defense. This chapter first asks: if defense against non-responsible threats and justified or innocent aggressors can be justified at all, how can it be justified? The chapter argues that the justified infringement or self-preference account (most prominently featured by Jonathan Quong) is implausible and that the competing liability account is to be preferred. The chapter then asks whether defense against non-responsible threats and justified aggressors is in fact justified. It gives a tentatively positive answer with regard to non-responsible threats, but argues that this answer can legitimately vary from one society to another or even be indeterminate. It also makes clear that non-responsible threats do not actually trigger a self-defense justification proper, but merely the normatively very different defensive emergency justification. The chapter then argues that self-defense against justified attackers is definitely permissible, which has important implications for the ethics of war. Opposing this view, Jeff McMahan and Victor Tadros argue that justification defeats liability and that hence there is no permissible defense against justified attackers. The chapter demonstrates that their and other arguments to this effect fail.