Case, a system which marks the relationships between words in a sentence, is fundamental to every language. Looking at how different theories of syntax have accounted for the distribution of case across languages, this accessible textbook introduces the various approaches to case that have been proposed in modern linguistics. Clearly organised into topics, it provides beginning students with a solid understanding of the ideas behind the development of theories of case. For the more advanced reader, it presents theories that have been formulated about the interaction between case morphology, argument structure, grammatical relations and semantics, and offers a detailed cross-theoretical discussion of how these are motivated. Each chapter contains practical exercises, encouraging students to engage with the ideas discussed. Drawing on data from a wide range of languages and pooling together a variety of perspectives, Theories of Case is essential reading for all those studying this important area of linguistics.