Batom Reachea III (Khmer: បទុមរាជាទី៣, born Ang Nan; 1654–1691) was a Cambodian vice king (uparaja) from 1682 to 1689.
Ang Nan fled to Thái Khang (present day Khánh Hòa Province of Vietnam), and sought help from Vietnamese Nguyễn lord.
Preah Keo II retreated into the forest and Ang Nan was crowned the vice king (uparaja) by the Vietnamese.
In 1682, he recruited refugees from Ming China who had settled in Cambodia with Vietnamese immigrants, resumed fighting against Chey Chettha IV.
In response, Kau Kan (Bassac, present day Sóc Trăng) and Preah Trapeang (Trà Vinh) were ceded to these Chinese adventures.