Anthropocene is a term that has been used to refer to the period of time during which humanity has become a planetary force of change. It appears in scientific and social discourse, especially with respect to accelerating geophysical and biochemical changes that characterize the 20th and 21st centuries on Earth. Originally a proposal for a new geological epoch following the Holocene, it was rejected as such in 2024 by the International Commission on Stratigraphy (ICS) and the International Union of Geological Sciences (IUGS).

The term has been used in research relating to Earth's water, geology, geomorphology, landscape, limnology, hydrology, ecosystems and climate. The effects of human activities on Earth can be seen, for example, in regards to biodiversity loss, and climate change. Various start dates for the Anthropocene have been proposed, ranging from the beginning of the Neolithic Revolution (12,000–15,000 years ago), to as recently as the 1960s. The biologist Eugene F. Stoermer is credited with first coining and using the term anthropocene informally in the 1980s; Paul J. Crutzen re-invented and popularized the term.

The Anthropocene Working Group (AWG) of the Subcommission on Quaternary Stratigraphy (SQS) of the ICS voted in 2016 to proceed towards a formal golden spike (GSSP) proposal to define an Anthropocene epoch in the geologic time scale. Later that year, the group presented the proposal to the International Geological Congress.

In 2019, the AWG voted in favour of submitting a formal proposal to the ICS by 2021. The proposal located potential stratigraphic markers to the mid-20th century. This time period coincides with the start of the Great Acceleration, a post-World War II time period during which global population growth, economic growth, pollution and exploitation of natural resources have all increased at a dramatic rate. The Atomic Age also started around the mid-20th century, when the risks of nuclear wars, nuclear terrorism, and nuclear accidents increased.

Twelve candidate sites were selected for the GSSP; the sediments of Crawford Lake (Halton Region), Canada were finally proposed, in 2023, to mark the lower boundary of the Anthropocene, starting with the Crawfordian stage/age in 1950.

In 2024, after 15 years of deliberation, the Anthropocene Epoch proposal of the AWG was voted down by a wide margin by the SQS, owing largely to its shallow sedimentary record and extremely recent proposed start date. The ICS and the IUGS later formally confirmed, by a near unanimous vote, the rejection of the AWG's Anthropocene Epoch proposal for inclusion in the Geologic Time Scale. The IUGS statement on the rejection concluded: "Despite its rejection as a formal unit of the Geologic Time Scale, Anthropocene will nevertheless continue to be used not only by Earth and environmental scientists, but also by social scientists, politicians and economists, as well as by the public at large. It will remain an invaluable descriptor of human impact on the Earth system."

As early as 1873, the Italian geologist Antonio Stoppani acknowledged the increasing power and effect of humanity on the Earth's systems and referred to an 'anthropozoic era'. From 1877 onward, the term 'Psychozoic' was used by geologists such as Joseph LeConte and Johannes Herman Frederik Umbgrove.

An early concept for the Anthropocene was the Noosphere by Vladimir Vernadsky, who in 1938 wrote of "scientific thought as a geological force". Scientists in the Soviet Union appear to have used the term Anthropocene as early as the 1960s to refer to the Quaternary, the most recent geological period. Ecologist Eugene F. Stoermer subsequently used Anthropocene with a different sense in the 1980s and the term was widely popularised in 2000 by atmospheric chemist Paul J. Crutzen, who regarded the influence of human behavior on Earth's atmosphere in recent centuries as so significant as to constitute a new geological epoch.