The country involved in the Opium Wars with Britain in the 19th century was China. The two wars, occurring between 1839-1842 and 1856-1860, were largely rooted in disputes over trade, particularly Britain's opium exports to China. The Chinese government's efforts to suppress the opium trade, which was causing significant social and health issues, led to conflict with Britain, whose economic interests were at stake. The resulting treaties, especially the Treaty of Nanking, imposed unequal terms on China, leading to territorial concessions, increased foreign influence, and significant social upheaval, marking a critical period in modern Chinese history.