尿失禁（英语：urinary incontinence，缩写作UI，或 involuntary urination），又称小便失禁，指尿液不自主地流出。尿失禁是一个普遍令人愁苦和尴尬的问题，会对患者的生活质量产生很大的影响。按照症状可分为充溢性尿失禁无阻力性尿失禁，反射性尿失禁，急迫性尿失禁及压力性尿失禁5类。尽管尿失禁是一种可以治疗的病理现象，但是由于这会引发尴尬等心理因素，患者很少就医。

Urinary incontinence (UI), also known as involuntary urination, is any leakage of urine. It is a common and distressing problem, which may have a large impact on quality of life. Urinary incontinence is often a result of an underlying medical condition but is under-reported to medical practitioners. Enuresis is often used to refer to urinary incontinence primarily in children, such as nocturnal enuresis (bed wetting).