尿苷（Uridine）是一种属于核苷的化合物，由尿嘧啶与核糖（呋喃核糖）环组成，两者由β-N₁-配糖键相连。

Uridine is a glycosylated pyrimidine-analog containing uracil attached to a ribose ring (or more specifically, a ribofuranose) via a β-N₁-glycosidic bond.

It is one of the five standard nucleosides which make up nucleic acids, the others being adenosine, thymidine, cytidine and guanosine. The five nucleosides are commonly abbreviated to their one-letter codes U, A, T, C and G respectively. However, thymidine is more commonly written as 'dT' ('d' represents 'deoxy') as it contains a 2'-deoxyribofuranose moiety rather than the ribofuranose ring found in uridine. This is because thymidine is found in deoxyribonucleic acid (DNA) and not ribonucleic acid (RNA). Conversely, uridine is found in RNA and not DNA. The remaining three nucleosides may be found in both RNA and DNA. In RNA, they would be represented as A, C and G whereas in DNA they would be represented as dA, dC and dG.