Greater India, also known as the Indian cultural sphere, the Indosphere, or the Indic world, is an area composed of many countries and regions in South and Southeast Asia that were historically influenced by Indian culture, which itself formed from the various distinct indigenous cultures of these regions. Specifically Southeast Asian influence on early India had lasting impacts on the formation of Hinduism and Indian mythology. Hinduism itself formed from various distinct folk religions, which merged during the Vedic and subsequent periods. The term Greater India, as a reference to the Indian cultural sphere, was popularised by a network of Bengali scholars in the 1920s. It is an umbrella term encompassing the Indian subcontinent and surrounding countries, which are culturally linked through a diverse cultural cline. These countries have been transformed to varying degrees by the acceptance and introduction of cultural and institutional elements from each other. Since around 500 BCE, Asia's expanding land and maritime trade had resulted in prolonged socio-economic and cultural stimulation and diffusion of Hindu and Buddhist beliefs into the region's cosmology, in particular in Southeast Asia and Sri Lanka. In Central Asia, the transmission of ideas was predominantly of a religious nature.
By the early centuries of the common era, most of the principalities of Southeast Asia had effectively absorbed defining aspects of Hindu culture, religion, and administration. The notion of divine god-kingship was introduced by the concept of Harihara, and Sanskrit and other Indian epigraphic systems were declared official, like those of the south Indian Pallava dynasty and Chalukya dynasty. These Indianized kingdoms, a term coined by George Cœdès in his work Histoire ancienne des états hindouisés d'Extrême-Orient, were characterized by resilience, political integrity, and administrative stability.
To the north, Indian religious ideas were assimilated into the cosmology of Himalayan peoples, most profoundly in Tibet and Bhutan, and merged with indigenous traditions.