Sindhudurg (Marathi: सिंधुदुर्ग जिल्हा) is an administrative district in the state of Maharashtra in India, which was carved out of the erstwhile Ratnagiri District. The district headquarters are located at Oros (ओरस). The district occupies an area of 5207 km² and has a population of 868,825 of which 9.47% were urban (as of 2001). [1]

As of 2011 it is the least populous district of Maharashtra (out of 39).

The district is named after the fort of Sindhudurg (which means "fort in the sea"), which lies on a rocky island just off the coast of Malvan (मालवण).

Sindhudurg district was established in 1981.

Sindhudurg is bordered on the north by Ratnagiri District, on the south by the state of Goa, on the west by the Arabian Sea, and to the east across the crest of the Western Ghats or Sahyadris is Kolhapur District. Sindhudurg is part of Konkan (coastal) region, a narrow coastal plain in western Maharashtra which lies between the Western Ghats and the Arabian Sea.

Sindhudurg has a semi-tropical climate and remains warm and humid in most of the year. It has three clear seasons : Rainy (June - October), winter (November-mid February) and Summer (mid February–May). Temperatures vary between Max. 32°C and monsoon winds bring heavy rains (average rainfall 3240.10 mm).

Sindhudurg (Marathi सिंधुदुर्ग) is a fortress which occupies an islet in the Arabian Sea, just off the coast of Maharashtra in western India. The fortress lies on the shore of Malwan town of Sindhudurg District in the Konkan region of Maharashtra, south of Mumbai. It is a protected monument.

Sindhudurg (sindhu = sea, durg = fort) was built by the great Maratha warrior King Shivaji in 1664. Shivaji selected the strategic rocky island location, then known as 'Kurte' for the fort ,himself - to counter foreign forces, and to keep the nearby Siddis of Murud-Janjira in check.

One of the best preserved forts of the Marathas, Sindhudurg fort has zigzag rampart with 42 bastions. Apart from the huge stones, the building material involved 2000 khandis (72,576 kg) of iron erecting the massive curtain wall and bastions. A notable feature is that the foundation stones were laid down firmly with 5 khandis (181.5 kg) of molten lead.

Over 4000 mounds of iron were used in the casting and foundation stones were firmly laid down. Construction started on 25 November 1664. Built over a period of three years (1664–67), the sea fort is spread over 48 acres (190,000 m²) with a two-mile (3 km) long rampart, and walls that are 30 feet (9.1 m) high and 12 feet (3.7 m) thick. The massive walls were designed to serve as a deterrent to approaching enemies and to the waves and tides of the Arabian Sea. The main entrance is concealed in such a way that no one can pinpoint it from outside.