The petroleum industry, also known as the oil industry or the oil patch, includes the global processes of exploration, extraction, refining, transportation (often by oil tankers and pipelines), and marketing of petroleum products. The largest volume products of the industry are fuel oil and gasoline (petrol). Petroleum is also the raw material for many chemical products, including pharmaceuticals, solvents, fertilizers, pesticides, synthetic fragrances, and plastics. The industry is usually divided into three major components: upstream, midstream, and downstream. Upstream regards exploration and extraction of crude oil, midstream encompasses transportation and storage of crude, and downstream concerns refining crude oil into various end products.

Petroleum is vital to many industries, and is necessary for the maintenance of industrial civilization in its current configuration, making it a critical concern for many nations. Oil accounts for a large percentage of the world’s energy consumption, ranging from a low of 32% for Europe and Asia, to a high of 53% for the Middle East.

Other geographic regions' consumption patterns are as follows: South and Central America (44%), Africa (41%), and North America (40%). The world consumes 36 billion barrels (5.8 km³) of oil per year, with developed nations being the largest consumers. The United States consumed 18% of the oil produced in 2015. The production, distribution, refining, and retailing of petroleum taken as a whole represents the world's largest industry in terms of dollar value.

The oil and gas industry spends only 0,4% of its net sales for Research & Development which is in comparison with a range of other industries the lowest share.

Governments such as the United States government provide a heavy public subsidy to petroleum companies, with major tax breaks at various stages of oil exploration and extraction, including the costs of oil field leases and drilling equipment.

In recent years, enhanced oil recovery techniques — most notably multi-stage drilling and hydraulic fracturing ("fracking") — have moved to the forefront of the industry as this new technology plays a crucial and controversial role in new methods of oil extraction.