The Noor-ul-Ain (Persian: نور العين, lit. 'the light of the eye') is one of the largest pink diamonds in the world, and the centre piece of the tiara of the same name.

The diamond is believed to have been recovered from the mines of Golconda, Hyderabad in India. It was first in possession with the nizam Abul Hasan Qutb Shah; later it was given as a peace offering to the Mughal emperor Aurangazeb when he defeated him in a siege. It was brought into the Iranian Imperial collection after the Persian king Nader Shah Afshar looted Delhi in the 18th century.^{[citation needed]}

The Noor-ul-Ain is believed to have once formed part of an even larger gem called the Great Table diamond. That larger diamond is thought to have been cut in two, with one section becoming the Noor-ul-Ain and the other the Daria-i-Noor diamond. Both of these pieces are currently part of the Iranian Crown Jewels.^[1]

The Noor-ul-Ain is the principal diamond mounted in a tiara of the same name made for Iranian Empress Farah Pahlavi's wedding to Shah Mohammad Reza Pahlavi in 1958. The tiara was designed by Harry Winston. It is a modern design, featuring 324 pink, yellow, and white diamonds set in platinum. It is said to weigh around 2 kg (4.4 lb). The tiara forms part of the Iranian crown jewels, held at the National Treasury of Iran in the Central Bank in Tehran.^{[citation needed]}

It is a Type IIa diamond.^{[citation needed]}

• Great Table diamond
• Koh-i-Noor diamond
• List of diamonds
• List of largest rough diamonds