Hyder Ali (c. 1720 – 7 December 1782, 2 Muharram 1197 in the Islamic calendar) is the de facto ruler of the Kingdom of Mysore in southern India.

Born Hyder Naik, he distinguishes himself militarily, eventually drawing the attention of Mysore's rulers.

Rising to the post of dalwai, or commander-in-chief to Krishnaraja Wodeyar II, he comes to dominate the titular monarch and the Mysore government, and eventually seizes control of all of the reins of power.

He expands the kingdom's borders at the expense of the Maratha Empire and Nizam of Hyderabad (among others), and is one of the few local rulers to effectively blunt the military advances of the British East India Company during two wars.

In the First and Second Anglo-Mysore Wars he comes within striking distance of the British outpost at Madras.

He is given a number of honorific titles, and is referred to as Sultan Hyder Ali Khan or Hyder Ali Sahib.

Hyder's rule of Mysore is characterized by frequent warfare with his neighbors and rebellion within his territories.

This is not unusual for the time, as much of the Indian subcontinent is at this time in turmoil, with the Hindu Maratha Confederacy struggling with the remnants of the Muslim Mughal Empire.

A shrewd leader, he leaves his son Tipu Sultan with a significantly enlarged kingdom.

He organizes his military in part along European lines, and is a pioneer in the military use of rocket artillery.

He has at least two wives, and fathers at least three children.