Thatta (ٺٽو, IPA: [ʈɦəʈːoː]; , IPA: [ʈɦəʈːɑː]) is a city in the Pakistani province of Sindh. Thatta was the medieval capital of Sindh, and served as the seat of power for three successive dynasties. Thatta's historic significance has yielded several monuments in and around the city. Thatta's Makli Necropolis, a UNESCO World Heritage Site, is site of one of the world's largest cemeteries and has numerous monumental tombs built between the 14th and 18th centuries designed in a syncretic funerary style characteristic of lower Sindh. The city's 17th century Shah Jahan Mosque is richly embellished with decorative tiles, and is considered to have the most elaborate display of tile work in the South Asia.
Thatta refers to riverside settlements. Villagers in the rural areas of lower Sindh often refer to the city as Thatta Nagar, or simply Nagar.
Thatta may be the site of ancient Patala, the main port on the Indus in the time of Alexander the Great, though the site of Patala has been subject to much debate. Muhammad bin Qasim captured the region in 711 CE after the defeating the local Raja in a battle north of Thatta. Thatta is reported by some historians to have been the ancient seaport of Debal that was mentioned by the Arab conquerors, though others place the seaport at the site of modern Karachi. At the time of the Umayyad conquests, small semi-nomadic tribes were living in the Sindh region. The Umayyad conquest introduced the religion of Islam into the hitherto mostly Hindu and Buddhist region.
Following Mahmud of Ghazna's invasion of Sindh in the early 11th century, the Ghaznavids installed Abdul Razzaq as Governor of Thatta in 1026. Under the rule of the Ghaznavids the local chieftain Ibn Sumar, then ruler of Multan, seized power in Sindh and founded the Sumra dynasty, which ruled from Thatta from 1051 for the next 300 years. Under Sumra rule, Thatta's Ismaili Shia population was granted special protection. The Sumra dynasty began to decline in power by the 13th century, though Thatta and the Indus Delta remained their last bastions of power until the mid 14th century.