The district of Monthey is a district of the canton of Valais in Switzerland. It has a population of 47,912 (as of 31 December 2020).

It comprises the following municipalities:

The blazon of the municipal coat of arms and flag is Or, issuant from coupeaux Vert an Oak-tree proper leaved and fructed of the second.

Monthey has a population (as of December 2020) of 47,912. In 2000, most of the population spoke French (29,275 or 87.7%) as their first language; German was the second most common (874 or 2.6%) and Italian was the third (808 or 2.4%). There were 14 people who speak Romansh.

As of 2008, the gender distribution of the population was 49.7% male and 50.3% female.