Petrochemicals are chemical products made from the hydrocarbons present in raw natural gas and petroleum crude oil. The largest ical manufacturing industries are to be
found in the United States, Western Europe, Asia and the Middle East.
A relatively small number of hydrocarbon feedstocks form the basis of the petrochemical industries, namely methane, ethylene, propylene, butanes, butadiene, benzene, toluene and xylenes. 
As of 2007, there were 2,980 operating petrochemical plants in 4,320 locations worldwide. The petrochemical end products from those plants include plastics, soaps, detergents, solvents, paints, drugs, fertilizer, pesticides, explosives, synthetic textile fibers and rubbers, flooring and insulating materials and much more.
Petrochemicals are found in such common consumer products as aspirin, cars, clothing, compact discs, video tapes, electronic equipment, furniture, and a great many others. Complete petrochemical plant in Teeside, UK
- Methane, ethane, propane and butanes: Obtained primarily from natural gas processing plants.
- Naphtha: Obtained from petroleum refineries.
- Benzene, toluene and xylenes, as a whole referred to as ''BTX'': Primarily obtained from petroleum refineries by extraction from the reformate produced in catalytic reformers.
- Gas oil: Obtained from petroleum refineries.
Methane and BTX are used directly as feedstocks for producing petrochemicals. However, the ethane, propane, butanes, naphtha and gas oil serve as optional feedstocks for steam-assisted thermal cracking plants referred to as ''steam crackers'' that produce these intermediate petrochemical feedstocks:
- Butenes and butadiene
- Benzene Petrochemical feedstock sources
In 2007, the amounts of ethylene and propylene produced in steam crackers were about 115 Mt (megatonnes) and 70 Mt, respectively. The output ethylene capacity of large steam crackers ranged up to as much as 1.0 – 1.5 Mt per year. 
Steam crackers are not to be confused with steam reforming plants used to produce hydrogen and ammonia.
As of 2004, the percentage of the worldwide steam cracking plants using each of the optional steam cracking feed sources was:
- Ethane: 35%
- Propane: 9%
- Butanes: 3%
- Naphtha: 45%
- Gas oil: 5%
- Other: 3 %
The table below includes some representative examples of the petrochemical end products produced from the eight hydrocarbon feedstocks – methane, ethylene, propylene, butenes, butadiene, benzene, toluene and xylenes:
- ^ Sami Matar and Lewis F. Hatch (2001), Chemistry of Petrochemical Processes, Gulf Professional Publishing, ISBN 0-0-88415-315-0
- ^ Staff (March, 2001), "Petrochemical Processes 2001", Hydrocarbon Processing, pp. 71-246, ISSN 0887-0284
- ^ Petrochemical Industry – Worldwide
- ^ Petrochemicals Chart From the website of the National Petrochemical & Refiners Association
- ^ Same as Reference 1
- ^ Same as Reference 2
- ^ SBS Polymer Supply Outlook
- ^ Editor: Jean-Pierre Favennec (2001), Petroleum Refining: Refinery Operation and Management, Editions Technip, ISBN 2-7108-0801-3
- ^ Editors: Hassan E. Alfadala, G.V. Rex Reklaitis and Mahmoud M. El-Halwagi (2009), Proceedings of the 1st Annual Gas Processing Symposium, Volume 1: January, 2009 - Qatar, 1st Edition, Elsevier Science|pages, pp. 402-414, ISBN 0-444-53292-7
- ^ Cracker capacities From the website of the Association of Petrochemicals Producers in Europe (APPE)
- ^ Steam Cracking: Ethylene Production (pdf page 3 of 12 pdf pages)
- ^ Richard Meyers (2003), The Basics of Chemistry, Greenwood Press, ISBN 0-313-31664-3
- Milton Beychok