The Second Anglo-Mysore War (1780-1784) was a conflict in India between the Kingdom of Great Britain and the Kingdom of Mysore. At the time, Mysore was a key French ally in India, and the Franco-British conflict raging on account of the American Revolutionary War helped spark Anglo-Mysorean hostilities in India.

Haidar Ali was ruler of Mysore (though he did not have the title of king). Stung by a British breach of faith during an earlier war against the Marathas, Haidar committed himself wholeheartedly to the French alliance and to revenge against the British. On the French declaration of war against Britain in 1778, the British (then firmly entrenched in Madras) resolved to drive the French out of India. The British captured of Mahé on the coast of Malabar in 1779, and annexed certain lands belonging to a dependent of Haidar's.

Haidar 'Ali sprung at the opportunity to strike back, and suceeded in making himself master of all that the Marathas had taken from him. With an empire extended to the Krishna River, he descended through the passes of the Ghats amid burning villages, reaching Conjeeveram, only 45 miles from Madras, unopposed. Not till the smoke was seen from St Thomas' Mount, where Sir Hector Munro commanded some 5200 troops, was any movement made; then, however, the British general sought to effect a junction with a smaller body under Colonel Baillie recalled from Guntur. The incapacity of these officers, notwithstanding the splendid courage of their men, resulted in the total destruction of Baillie's force of 2800 (September 10, 1780).

Warren Hastings sent from Bengal Sir Eyre Coote, who, though repulsed at Chidambaram, defeated Haidar three times in succession in the battles of Porto Novo, Pollilur and Sholingarh, while Tipu was forced to raise the siege of Wandiwash, and Vellore was provisioned. Tipu defeated Brathwaite on the banks of the Coleroon in February 1782. On the arrival of Lord Macartney as governor of Madras, the British fleet captured Negapatam, and forced Hyder Ali to confess that he could never ruin a power which had command of the sea. He had sent his son Tipu to the west coast, to seek the assistance of the French fleet, when his death took place suddenly at Chittur in December 1782. The young Tipu Sultan therefore took over the war effort.

The British captured Coimbatore in 1783, but neither they nor Mysore were able to obtain a clear overall victory. The war was ended in 1784 with the Treaty of Mangalore , at which both sides agreed to restore the others' lands to the status quo ante bellum.

This was the second of four Anglo-Mysore Wars.