The Duchy of Surabaya (Indonesian and Javanese: Kadipaten Surabaya) was a Javanese principality centered in Surabaya, on the northeastern coast of Java (in today's East Java, Indonesia), that existed as an independent polity from c. 1546 to 1625. It became independent following the disintegration of the Demak Sultanate, and by the beginning of the 17th century had become the leading power in east Java and the most important port on Java's northeastern coast. Subsequently, it entered into decades of conflict with the Mataram Sultanate that ended in the victory of Mataram and the fall of Surabaya in 1625.

The Portuguese writer Tomé Pires mentioned that a Muslim lord was in power in Surabaya in 1513 though likely a vassal of the Hindu–Buddhist Majapahit. At that time, Surabaya was already a major trading port, owing to its location on the River Brantas delta and on the trade route between Malacca and the Spice Islands via the Java Sea. During the decline of Majapahit, the lord of Surabaya resisted the rise of the Demak Sultanate, and only submitted to its rule in 1530. Surabaya became independent after the death of Sultan Trenggana of Demak in 1546. There is a dearth of historical records about the duchy in the second half of the 16th century. In 1589 Surabaya led other east Javanese principalities in opposing the Pajang Sultanate, Demak's successor state, in Japan (today's Mojokerto), thereby stopping Pajang's eastward expansion. Javanese historians said that a holy man, a descendant of Sunan Giri, convinced the opposing sides to return without a battle. Dutch historian H. J. de Graaf wrote that in the second half of 16th century, the court of Surabaya became a centre of culture and Islamic Old Javanese literature, as opposed to the "upstart" central Javanese courts such as the Pajang and Mataram Sultanates.

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