乌多姆塞省（老挝语：ອຸດົມໄຊ，拉丁字母：Oudomxai）是老挝西北部的一个省，首府芒赛。

这里最早的居民是克木族，在1260年来自西双版纳的泰人征服该地，并创建一条名为Ban Luang Cheng的村落。

Oudomxay (alternates: Oudômxai or Moung Xai; Lao:ອຸດົມໄຊ) is a province of Laos, located in the northwest of the country. The province capital is Muang Xai.

Oudomxay Province covers an area of 15,370 square kilometres (5,930 sq mi). The province borders China to the north, Phongsali Province to the northeast, Luang Prabang Province to the east and southeast, Xaignabouli Province to the south and southwest, Bokeo Province to the west, and Luang Namtha Province to the northwest. The topography of Oudomxay is mountainous, between 300–1,800 metres (980–5,910 ft) above sea level.