The Long Beach Oil Field is a large oil field underneath the cities of Long Beach and Signal Hill, California, in the United States. Discovered in 1921, the field was enormously productive in the 1920s, with hundreds of oil derricks covering Signal Hill and adjacent parts of Long Beach; largely due to the huge output of this field, the Los Angeles Basin produced one-fifth of the nation's oil supply during the early 1920s. In 1923 alone the field produced over 68 million barrels of oil, and in barrels produced by surface area, the field was the world's richest. The field is eighth-largest by cumulative production in California, and although now largely depleted, still officially retains around 5 million barrels of recoverable oil out of its original 950 million. 294 wells remained in operation as of the beginning of 2008, and in 2008 the field reported production of over 1.5 million barrels of oil. The field is currently run entirely by small independent oil companies, with the largest operator in 2009 being Signal Hill Petroleum, Inc.

Long Beach is a city in Los Angeles County, California, United States. It is the 43rd-most populous city in the United States, with a population of 466,742 as of 2020. A charter city, Long Beach is the seventh-most populous city in California, the second most populous city in Los Angeles County, and the largest city in California that is not a county seat city.