<p>This study examines the evolution of state societies and the assertion of royal legitimacy in the early Brahmaputra Valley, with a focus on the region that comprises modern-day Assam in northeastern India. Moving beyond conventional interpretations, this analysis employs Integrative and Processual polity models to demonstrate how state formation in peripheral regions involved dynamic processes of territorial expansion and cultural synthesis. The valley’s early history, documented through epigraphic evidence, archaeological remains, and literary sources from the 4th to 13th centuries CE, reveals a complex socio-political landscape characterized by multiple state systems, agricultural development, and legitimation strategies. The Brahmaputra Valley’s ecological characteristics also provided the material foundation for distinctive patterns of state formation. The region is characterized by a broad alluvial plain carved by the Brahmaputra River and its tributaries, hemmed in by highlands on almost all sides. The study challenges traditional historiographical perspectives that perceived early Assam states as centralized bureaucratic entities by addressing processes of horizontal integration, tribal accommodation, and environmental adaptation that created distinctive patterns of political development. Through systematic analysis of over thirty inscriptions, recent archaeological discoveries, and comparative analysis with contemporary regional developments, this research contributes to Early Medieval Indian historiography by providing a theoretically grounded understanding of how peripheral regions participated in broader subcontinental patterns while maintaining unique characteristics shaped by local ecological, cultural, and political factors.</p>