The Sultanate of Muscat and Oman (Arabic: سلطنة مسقط وعمان Salṭanat Masqaṭ wa-‘Umān) was a thalassocratic nation that encompassed the present-day Sultanate of Oman and parts of present-day United Arab Emirates and Gwadar, Pakistan. The country is not to be confused with Trucial Oman, which were sheikhdoms under British protection since 1820.
In the early 1820s, the Sultanate lost most of its territories in the Persian Gulf, which became the Trucial States under British protection. The fifth Sultan of the Al Said dynasty, Said bin Sultan, consolidated the Sultanate's territorial holdings and economic interests and Oman prospered. However, the Omani fleet was unable to compete with the more technically advanced European fleets and the Sultanate lost much of the trade with South Asia. Pressure by the British to abandon the slave trade further led to the loss of political and economic clout of the Sultanate.
On June 4, 1856, Said bin Sultan died without appointing an heir to the throne and members of the Al Said dynasty could not agree on a ruler. Through British mediation, two rulers were appointed from the Al Said clan; the third son of the Sultan, Thuwaini bin Said became ruler of the mainland. His sixth son, Majid bin Said, became ruler of an independent Sultanate of Zanzibar on October 19, 1856. The Sultans of Zanzibar were thereafter obliged to pay an annual tribute to Muscat.
The Sultanate of Muscat was regularly under attack from the devout Ibadi tribes who resented the influence of the more secular coastal people. The Sultanate was however able to defend itself with British help. This historical split continued throughout much of the twentieth century with Sultan Taimur bin Feisal granting limited autonomy to the Imamate of Oman under the Ibadi clergy through the Treaty of Seeb in 1920.
The last overseas possession, the port of Gwadar across the Gulf of Oman, was sold to Pakistan in 1958. However, the sultanate did gain some territory in 1967, when Britain returned the Khuriya Muriya Islands (originally granted as a gift from the sultan to Queen Victoria in 1854).