Peak oil is the hypothetical point in time when the maximum rate of global oil production is reached, after which it is argued that production will begin an irreversible decline. It is related to the distinct concept of oil depletion; while global petroleum reserves are finite, the limiting factor is not whether the oil exists but whether it can be extracted economically at a given price. A secular decline in oil extraction could be caused both by depletion of accessible reserves and by reductions in demand that reduce the price relative to the cost of extraction, as might be induced to reduce carbon emissions.

Numerous predictions of the timing of peak oil have been made over the past century before being falsified by subsequent growth in the rate of petroleum extraction. M. King Hubbert is often credited with introducing the notion in a 1956 paper which presented a formal theory and predicted U.S. extraction to peak between 1965 and 1971. Hubbert's original predictions for world peak oil production proved premature and, as of 2021, forecasts of the year of peak oil range from 2019 to 2040. These predictions are dependent on future economic trends, technological developments, and efforts by societies and governments to moderate climate change.

Predictions of future oil production made in 2007 and 2009 stated either that the peak had already occurred, that oil production was on the cusp of the peak, or that it would occur soon. A decade later world oil production rose to hit a new high in 2018, as developments in extraction technology enabled an expansion of U.S. tight oil production. Following a collapse in oil demand at the outset of the COVID-19 pandemic and a price war between Saudi Arabia and Russia, a number of organizations have put forward predictions of a peak in the next 10 to 15 years.