This book offers fresh perspectives on “shared grammaticalization”, a state whereby two or more languages have the source and the target of a grammaticalization process in common. While contact-induced grammaticalization has generated great interest in recent years, far less attention has been paid to other factors that may give rise to shared grammaticalization. This book intends to put this situation right by approaching shared grammaticalization from an integrated perspective, including areal as well as genealogical and universal motivations and by searching for ways to distinguish between these factors. The volume offers a wealth of empirical facts, presented by internationally renowned specialists, on the Transeurasian languages (i.e. Japonic, Koreanic, Tungusic, Mongolic, and Turkic) — the languages in focus —as well as on various other languages.