Kut Ruea (Thai: กุดเรือ) is a tambon (subdistrict) located in the southernmost area of Thung Si Udom district, in Ubon Ratchathani Province, Thailand.

[1] Neighbouring subdistricts are (clockwise from the south) Khilek, Kut Salao, Khok Chamrae, Na Kasem, and Kaeng.

[2] The tambon was founded in 1985 by incorporating seven settlements in the western part of Kaeng in the Det Udom district.

[3] Later in 1992, tambon Kut Ruea, together with four other subdistricts, including Thung Thoeng, Na Kasem, Nong Om, and Khok Chamrae, were split off from Det Udom district to create a minor district (king amphoe) called Thung Si Udom.

[4] However, the inclusion of tambon Thung Thoeng into the new district was undone a year later, on June 1.