Na Noi (Thai: นาน้อย, pronounced [nāː nɔ́ːj]) is a district (amphoe) in Nan Province, northern Thailand.
Na Noi was originally named Wiang Si Sa Ket (เวียงศรีษะเกษ). In 1899 it became part of Nan Province. Though it was originally planned to merge Sisaket and Tha Pla Subdistrict into one district, in 1903 Tha Pla was merged into Uttaradit Province. In 1917 the name of the district was changed, to avoid confusion with Sisaket Province.