Mont Belvieu is a city in Chambers County in the U.S. state of Texas. It is just north of Interstate 10 along State Highway 146. The population is currently 11,922 and was 7,654 at the 2020 census, an increase of nearly 100% from 3,835 in 2010. It is the site of the largest underground storage facility for liquefied petroleum gas in the US. The US LPG market pricing indicator is driven primarily by the Mont Belvieu market, and reported daily by the US Energy Administration.