Thuwaini bin Said
Sultan of Muscat and Oman
Reign	1856–1866
Predecessor	Said bin Sultan
Successor	Salim bin Thuwaini
Born	1821 Muscat, Oman
Died	11 February 1866(1866-02-11) (aged 44–45) Sohar Fort
Burial	Al Hujra
Spouse	Ghaliya bint Salim al Busaidiyah
Issue	Salim Harub Hamad Aliya
House	Al Said
Father	Said bin Sultan

Thuwaini bin Said al-Busaidi (Arabic: ثويني بن سعيد ال سعيد, Sayyid Ṯuwaynī bin Saʿīd Āl Saʿīd) (1821–1866) was Sultan of Muscat and Oman (19 October 1856 – 11 February 1866) and the third son of Said bin Sultan. Thuwaini was born in Oman, and never visited Zanzibar. When his father was away in Zanzibar, Thuwaini was his representative in Oman.

Thuwaini was married to his cousin Ralie (Sayyida Ghaliya bint Salim Al-Busaidiyah), daughter of his father's elder brother Salim Ibn Sultan. They had several children.^{[citation needed]}

After the death of Said bin Sultan on Zanzibar in 1856, Thuwaini became Sultan of Muscat and Oman, while his brother, the sixth son, Majid, took power on Zanzibar. Through British mediation, it was agreed that Majid should pay a yearly tribute to Oman. However, Majid paid this tribute for only a few years, and when he stopped, Thuwaini was in no position to enforce payment from the much wealthier Zanzibar. This left Muscat and Oman in a difficult financial situation. Thuwaini was forced to levy duties on various articles, creating malcontent. In 1866 he was rumored to have been killed by his own son, Sayyid Salim bin Thuwaini.

The Arabist scholar and traveller William Gifford Palgrave relates how, when they were shipwrecked in March 1863 on Sowadah Island just off Oman, they were very well received and treated by Thuwaini.

• Emily Ruete, Ulrich Haarmann (Editor), E. Van Donzel (Editor), Leiden, Netherlands, (1992): An Arabian Princess Between Two Worlds: Memoirs, Letters Home, Sequels to the Memoirs, Syrian Customs and Usages. ISBN 90-04-09615-9
• Palgrave, W. G. (1866): Personal Narrative of a Year's Journey through Central and Eastern Arabia (1862–1863), Vol. II, (full text available online, also reprinted many times)