Millions of Indians migrated internally within the British Empire during the 19th and 20th centuries. While some migrated as labor migrants, many others did so as merchants and other businesspeople. By the start of World War II, more than 200,000 Indians worked in trade outside of India. These merchants played key roles in the British Empire within India and the larger Indian Ocean economy. Several conditions facilitated and perhaps caused Indian merchant migration within the British Empire. First, precolonial Indian commerce continued and adapted to imperial trade patterns. Second, within India, British rule lowered transaction costs and opened markets. Third, British rule brought preferential access to British colonies outside India, access that was denied to merchants from outside the British Empire. Internal merchant migration within India shows the importance of distinct religious, caste, and linguistic groups, many of which were active before British control. Gujarati-speaking merchant migrants and Parsis were bulwarks of Bombay’s commercial class. Specific merchant communities migrated within trading networks across India as railroads connected the subcontinent. Outside India, merchants—often from these same groups—accompanied British expansion in Asia and Africa. In Burma and Malaya, Chettiars from the south formed banking and trading networks that tied these colonies closer to the Indian economy. Chettiar finance was crucial in the development of industry in both Burma and Malaya. Indian businesspeople dominated commerce in East Africa and played key roles in commerce. Indian businesses in Uganda developed local commercial agriculture and industry, and Indians in South Africa played a large role in commerce before legal restrictions reduced their involvement. Distant colonies in which indentureship was the dominant form of migration experienced a transition from labor to trade, with merchant migration playing a smaller role. These colonies do not fit the pattern of merchant migration seen in India and the larger Indian Ocean economy, but they illustrate the role of Indian tradespeople outside India.