Urea, also known as carbamide, is an organic compound with chemical formula CO(NH₂)₂. This amide has two amino groups (–NH₂) joined by a carbonyl functional group (–C(=O)–). It is thus the simplest amide of carbamic acid.

Urea serves an important role in the metabolism of nitrogen-containing compounds by animals and is the main nitrogen-containing substance in the urine of mammals. Urea is New Latin, from French urée, from Ancient Greek οὖρον (ouron, "urine"), itself from Proto-Indo-European *h₂worsom.

It is a colorless, odorless solid, highly soluble in water, and practically non-toxic (LD₅₀ is 15 g/kg for rats). Dissolved in water, it is neither acidic nor alkaline. The body uses it in many processes, most notably nitrogen excretion. The liver forms it by combining two ammonia molecules (NH₃) with a carbon dioxide (CO₂) molecule in the urea cycle. Urea is widely used in fertilizers as a source of nitrogen (N) and is an important raw material for the chemical industry.

In 1828 Friedrich Wöhler discovered that urea can be produced from inorganic starting materials, which was an important conceptual milestone in chemistry. This showed for the first time that a substance previously known only as a byproduct of life could be synthesized in the laboratory without biological starting materials, thereby contradicting the widely held doctrine of vitalism, which stated that only living organisms could produce the chemicals of life.