April 30, Iran marks Persian Gulf Day, commemorating the 403-year-old victory over a foreign colonial superpower that liberated the Iranian coast after a century of occupation.

The Persian Gulf is one of three seas along which Iran has coastlines—alongside the Caspian Sea and the Gulf of Oman—and is arguably the most significant among them.

Iran and the Persian Gulf share a continuous and intertwined history spanning more than two and a half millennia, occasionally disrupted by foreign attempts to assert dominance, all of which have ultimately failed.

Beneath its waters lies the world’s largest reservoir of oil and gas, and it also serves as a vital strategic hub through which a significant portion of Iran’s international trade is conducted.

Persian Gulf Day reminds the Iranian nation of the momentous events that shaped the region’s history, had a profound impact on Iran, and continue to offer important lessons for the present.

What does Persian Gulf Day represent?

Persian Gulf Day is an official holiday in the Islamic Republic of Iran that commemorates the liberation of its southern shores from Portuguese colonial occupation nearly 400 years ago.

Established in 2005 by Iran's Supreme Council of the Cultural Revolution, the day is observed annually with nationwide events celebrating the Persian Gulf's history, name, and strategic significance.

The 10th of Ordibehesht in the Iranian calendar—corresponding to April 29 or 30 in the Gregorian calendar—was chosen to mark this occasion.

On this day in 1622, then-Iranian ruler Abbas I of the Safavid dynasty defeated Portuguese forces on the island of Hormuz, bringing an end to a 20-year war and a century of foreign domination over the Persian Gulf.