A fertilizer or fertiliser is any material of natural or synthetic origin (other than limimng material) that is applied to soil or to plant tissues to supply one or more plant nutrient essential to the growth of plants. Many sources of fertilizer exist, both natural and industrially produced.

In the later half of the 20th century, increased use of nitrogen fertilizers (800% increase between 1961 and 2019) have been a crucial component of the increased productivity of conventional food system (more than 30% per capita). According to the IPCC Special Report on Climate Change and Land, these practices are key drivers of global warming.