Arun (Nepali: अरुण) is one of seven rural municipalities (गाउँपालिका) of Bhojpur District of Province No. 1 of Nepal. There are a total of 9 municipalities in Bhojpur of which 2 are urban and 7 are rural.

According to MoFALD Arun has an area of 154.76 square kilometres (59.75 sq mi) and the total population of the municipality is 17, 687 as of Census of Nepal 2011. Champe, Yangpang, Pyauli, Charambi, Jarayotar and Yaku VDCs were merged to form Arun Rural Municipality. Pyauli is the Headquarter of this newly formed rural municipality.