The Battle of Indus was fought at the river Indus in today's Pakistan in the year 1221 between Jelal ad-Din Mingburnu, the sultan of the Khwarezmid Empire and his only remaining forces of five thousand, and the Mongolian horde of Chinggis Khan.

Jelal ad-Din Mingburnu was fleeing to India with his men together with thousands of refugees from Persia, following the Mongol sacking of several cities, including Bukhara and Samarkand, the latter being the Khwarezmian capital. After having won the Battle of Parwan, near the city Ghazna (Ghazni) in eastern Persia, Mingburnu headed for India to seek refuge together with his army of some fifty thousand men and several thousand refugees. However, the horde of Chinggis Khan caught up with him when he was about to cross the river Indus, the border of India. The sultan posted most of his men in the way of the Mongols to let him and the refugees pass the river in safety. When the army who awaited the enemy was busy fighting the Mongolian vanguard, Chinggis Khan led the main force towards the sultan who was trapped between the Mongols and the river.

The sultan engaged the Mongols with his five thousand men against the Mongols' over ten thousand. This attempt failed however and the soldiers where soon separated from the refugees who were brutally slaughtered. When the sultan realised he was doomed, he and his closest followers crossed the river into India. Only a few of the refugees and probably none of the soldiers made it to the other side alive. Jelal ad-Din Mingburnu spent three years in exile in India before returning to Persia.