Kyawthuite is an extremely rare mineral with formula BiSbO<sub>4</sub>. It is a natural bismuth antimonate, in which bismuth has oxidation state +3, and antimony oxidation state +5.
The only known sample of kyawthuite is on display at the Natural History Museum of Los Angeles County.
Kyawthuite is monoclinic, with space group , and is isostructural with clinocervantite, its trivalent-antimony-analogue. Kyawthuite is an antimony-analogue of clinobisvanite.
Kyawthuite was discovered in the vicinity of Mogok in Myanmar, an area famous for its variety of gemstone minerals, in 2010 and was subsequently identified as being a new specimen by Dr. Kyaw Thu. The International Mineralogical Association officially recognised kyawthuite as a new mineral in 2015.
Only one 0.3-gram sample of the naturally occurring form of this mineral is documented, and it is stored and on display at the Natural History Museum of Los Angeles County.