A technofossil refers to geological evidence of human technological activity preserved in Earth's strata that will persist for millions of years. These anthropogenic materials form distinctive markers in the geological record, with many geologists, paleobiologists, and environmental researchers stating that they would provide future evidence of humanity's industrial and consumer-oriented civilization. Technofossils represent a significant aspect of the proposed Anthropocene epoch, characterized by humanity's profound geological impact on the planet due to the mass production of synthetic resources, modified biological remains, and chemical or radioactive markers.

The term "technofossil", first coined in 2014, describes manufactured or modified materials that possess sufficient durability to persist in Earth's geological record for millions of years. Unlike traditional biological fossils, technofossils result from human technological processes rather than natural and biological processes. These persistent artifacts form a distinctive stratigraphic signature that several geologists and environmental scientists state will remain identifiable to future geologists or intelligent entities examining Earth's history.

University of Leicester Department of Geology professors Jan Zalasiewicz, Mark Williams, and Sarah Gabbott, consider technofossils a defining characteristic of the Anthropocene. Each theorize that their durability and vast global distribution are in the process of creating an unprecedented geological signature distinct from all previous geological epochs. Williams described technofossils as eventually becoming the "defining imprint" of the Anthropocene, positing that future archaeologists would find the technofossil strata "more weird and wonderful, by far, than dinosaur bones."

Synthetic polymers, due to their exceptional durability, massive production volumes, and global distribution, have led geologists to characterize them as the most ubiquitous and enduring technofossils. Many synthetic polymers exhibit chemical stability comparable to certain natural fossilized materials. Such items include single-use plastic products, particularly from fast food and consumer goods, microplastics distributed throughout marine sediments, and synthetic fabrics and textiles incorporating plastic fibers.

Paleobiologists such as Zalasiewicz and Gabbott noted that certain ancient organic fossils, such as the cell walls of 50-million-year-old green algae and the organic tubes of graptolites, contain compounds chemically similar to modern polyethylene, suggesting the extraordinary longevity plastic materials will likely exhibit in the geological record.

Synthetic textiles persist much longer than traditional natural fibers like cotton, linen, and silk, which readily decompose without special preservation conditions. Landfills can effectively mummify discarded clothing, preserving these materials for potential technofossilization. The abrupt appearance of synthetic textiles would mark a clear stratigraphic boundary in the Earth's geological record, as they represent a complete departure from the millennia of biodegradable natural fiber production that preceded them. Modern textile production exceeds 100 billion garments annually, double the amount produced two decades ago.

Concrete, exceeding 500 billion tonnes and possesses intrinsic qualities conducive to technofossilization, represents humanity's most abundant manufactured material. The material's durability, and conditions such as urban centers in subsiding coastal areas, present ideal fossilization conditions. Environmental scientists state that concrete structures in cities like New Orleans, built below sea level, will eventually submerge beneath sediment, preserving foundations, seawalls, and infrastructure. Many geologists predict that these massive concrete deposits will create distinctive lithified zones within future rock strata, preserving the geometric and structural patterns of human civilization.

While pure metals themselves rarely persist in geological records due to their reactivity, many geologists predict that metallic products will leave distinctive impressions and mineral formations indicative of prior human civilization.