The First Anglo-Mysore War (1766-1769) was a war in India between the Kingdom of Mysore and the Kingdom of Great Britain.

Hyder Ali, ruler of Mysore, had begun to occupy the serious attention of the British government in Madras, which in 1766 entered into an agreement with the Nizam to furnish him with troops to be used against the common foe. But hardly had this alliance been formed when a secret arrangement was come to between the two Indian powers, the result of which was that Colonel Smith's small force was met with a united army of 50,000 men and 100 guns. British dash and sepoy fidelity, however, prevailed, first in the battle of Chengam (September 3, 1767), and again still more remarkably in that of Tiruvannamalai (Trinornalai).

On the loss of his recently made fleet and forts on the western coast, Hyder Ali now offered overtures for peace; on the rejection of these, bringing all his resources and strategy into play, he forced Colonel Smith to raise the siege of Bangalore, and brought his army within 5 miles of Madras. The result was the treaty of April 1769, providing for the mutual restitution of all conquests, and for mutual aid and alliance in defensive war.