This chapter examines the role and legal status of State lying in grey zone conflicts, focusing on States lying to other States in their inter-State communications. The chapter begins by examining the utility of State lying in grey zone conflicts, looking at the example of Russia’s 2014 annexation of Crimea. While there is presently no international law prohibition on State lying, the chapter argues that we should extend the existing laws on insincere State utterances to include lying by States. Because the existing laws are explained by the principle of good faith, the proposed prohibition on State lying would only apply when States are coordinating plans of action, creating problems for its application in grey zone conflicts. The chapter looks to resolve some of these difficulties, before concluding with a summary of the argument.