溃疡性结肠炎（英语：Ulcerative Colitis，缩写UC），也称非特异性溃疡性结肠炎，是炎症性肠病的一种。发病原因尚不明确，可能是一种自体免疫性疾病。

是炎症性肠病的一种（另一种常见炎症性肠病为克罗恩病），病灶局限于结肠粘膜及粘膜下层，多位于乙状结肠和直肠，也可延伸至降结肠，甚至整个结肠，一般不会累及小肠。

病人结肠粘膜呈充血、水肿，并可以形成多数大小不等、容易出血的溃疡，严重者大段结肠可无正常粘膜；症状有腹泻、腹痛、厌食、发热、消瘦及粪便有血等。

本病目前没有特别好的内科方法根治，病人常需长期用药维持，常反复发作。也有一些病人会采取外科手术“根治”该病。此病多发于20~30岁，影响患者生活质量。

Ulcerative colitis (UC) is a form of inflammatory bowel disease (IBD) that causes inflammation and ulcers in the colon. The disease is a type of colitis, which is a group of diseases that cause inflammation of the colon, the largest section of the large intestine, either in segments or completely. The main symptom of active disease is diarrhea mixed with blood. Ulcerative colitis has much in common with Crohn's disease, another form of IBD, but what sets it apart from Crohn's disease is that ulcerative colitis, as its name suggests, only affects the colon and rectum, rather than the whole GI tract. Ulcerative colitis is an intermittent disease, with periods of exacerbated symptoms, and periods that are relatively symptom-free. Although the symptoms of ulcerative colitis can sometimes diminish on their own, the disease usually requires treatment to go into remission.