The Diu Fortress is a Portuguese-built fortification located on the west coast of India in Diu. The fortress was built as part of Portuguese India's defensive fortifications at the eastern tip of the island of Diu during the 16th century. The fortress, which borders on the town of Diu, was built in 1535 subsequent to a defense alliance forged by Bahadur Shah, the Sultan of Gujarat and the Portuguese when Humayun, the Mughal Emperor attempted to annex this territory. It was strengthened over the years, till 1546. The Portuguese ruled over this territory from 1537 until the Indian invasion of December 1961. Today it is a landmark of Diu and one of the Seven Wonders of Portuguese Origin in the World.

Qutb-ud-Din Bahadur Shah, born Bahadur Khan was a sultan of the Muzaffarid dynasty who reigned over the Gujarat Sultanate, a late medieval kingdom in India from 1526 to 1535 and again from 1536 to 1537. He ascended to the throne after competing with his brothers. He expanded his kingdom and made expeditions to help neighbouring kingdoms. In 1532, Gujarat came under attack of the Mughal Emperor Humayun and fell. Bahadur Shah regained the kingdom in 1536 but he was killed by the Portuguese on board a ship when making a deal with them.