Deepwater Horizon, the name given to the oil spill from the British Petroleum (BP)-run Macondo Prospect in the Gulf of Mexico, occurred between April and September 2010. Macondo Prospect is a large area off the coast of the Louisiana that contains large deposits of oil and is thus the site of several oil drills. The oil spill began on April 20, 2010 when an oil platform was engulfed in flames following high pressure methane gas igniting and exploding on the Deepwater Horizon drilling rig. This explosion resulted in the suspected deaths of eleven workers whose bodies were never recovered and injuries to sixteen others. Two days after the explosion, the rig completely sank and an oil leak was discovered shortly thereafter.

The leak continued throughout the summer, releasing an estimated total of 4.9 million barrels of crude oil in the Gulf of Mexico. Multiple attempts were made to plug the leak, with the United States government, BP and other entities working together to attempt to prevent further damage to the Gulf of Mexico and Gulf Coast regions of Louisiana, Mississippi, Florida, Alabama and Texas. Intentional burns, containment efforts and attempts to seal the well were made in an effort to protect the wildlife in the region, as well as to reduce the spread of oil. The well was officially sealed on September 21, 2010.

Following the seal, a massive clean-up effort ensued in the Gulf Coast region of the United States. In addition to harming the ecosystem, the spill had a massive impact on the fishing, farming and tourism industries of the region. Human health concerns continue to be a concern for those living in the region into the present due to the contamination of drinking water, seafood and soil.

This oil spill was among the largest in history and in many ways was the largest, depending upon the criteria utilized – it is the largest accidental marine oil spill in recorded history at 4.9 million barrels (roughly 210 million gallons). The largest oil spill in terms of actual tons of oil spilled in North America occurred in 1910 when a pressurized oil well spewed oil in the Midway-Sunset Oil Field in Kern County, California for eighteen months. The largest intentional oil spill in history occurred in 1991 when Iraqi forces set fire to over 600 oil wells in Kuwait towards the end of the Persian Gulf War.