This volume draws on insights from a range of theoretical perspectives to explore objects, agreement, and their intersecting angles, based on novel data from multiple language families. The recent expansion of agreement theories has revealed new ways of integrating phenomena that affect objects and their relational and featural properties with conventional object markers, under a single 'agreement' umbrella. The contributions to this book present the major advances in these new angles of research into object agreement, and highlight in particular the shared conditions on objects undergoing agreement that are attested in a large number of genetically unrelated languages and language modalities. Following a detailed introduction, the chapters are organized into four parts that explore respectively the mechanics of object agreement, constraints on symmetry, features of object agreement, and issues relating to the left periphery. The volume's findings and the novel questions that they raise will be of interest to theoretical linguists, typologists, sign language researchers, and anyone working on the theoretical analysis of Amazonian, Bantu, Romance, Semitic, and Slavic languages.