This chapter describes the private enforcement of competition law, that is to say the situation where litigants take their disputes to a domestic court or, quite often, to arbitration. It will deal with the private enforcement of Articles 101 and/or 102 as a matter of EU law, with particular emphasis on the Damages Directive. It also describes private actions for damages and injunctions in the High Court and the UK Competition Appeal Tribunal. The chapter considers the use of competition law as a defence, for example to an action for breach of contract or infringement of an intellectual property right. The chapter concludes with a brief discussion of issues that can arise where competition law disputes are referred to arbitration rather than to a court for resolution.