This book focuses on the evolution of object clitic pronouns in the Romance languages. It aims to explore the empirical facets of cliticization and elaborate on the theoretical ramifications of the topic. On the empirical side, the book deals with data ranging from Latin to modern languages and less well-known dialects from all areas of Romance. Medieval vernaculars take centre stage both in the reconstruction of the evolution from Latin to Romance and in the modelling of clitic placement in the modern languages. Syntactic, phonological, and morphological aspects are examined, but the main focus is on syntactic placement, which is the hallmark of Romance clitics. On the theoretical side, the books engage with the previous literature, in particular with Generative literature. In recent decades, our understanding of Romance clitics has grown in symbiosis with the Generative theory, and the importance of most empirical findings cannot be fully appreciated without being acquainted with the terms of the ongoing debate. The book challenges the received idea that cliticization resulted from a form of syntactic deficiency. Instead, it proposes that clitics resulted from the feature endowment of discourse features, which caused freezing of certain pronominal forms first and—through reanalysis—their successive incorporation into verbal hosts. This approach entails revising analyses of well-known phenomena such as interpolation, climbing, and enclisis/proclisis alternations (the so-called Tobler-Mussafia law), and addressing orthogonal phenomena such as V2 syntax, scrambling, and stylistic fronting.