The global oil and gas industry continues to be battered by one of the worst downturns in 30 years, as the perfect storm of overproduction and geopolitical tensions have seen oil prices plunge. In fact, every company on our 2018 list of the largest oil and gas companies in the world saw their revenue totals decrease compared to two years ago. This article takes a look at the largest oil and gas companies by market value located in this country. Leading Oil And Gas Companies In The US 1. ExxonMobil. ExxonMobil is the leading oil and gas company of the US with a market value of 356.5 billion. Additionally, it is the 7th largest company in the world by revenue. World Oil provides daily news, trends and data for the global upstream industry, including in-depth coverage of deepwater, subsea, shale, exploration, drilling, well completion, unconventionals