风疹（英语：rubella, German measles, three-day measles），又称德国麻疹或三日麻疹，是一种由风疹病毒感染所造成的疾病。风疹的症状轻微，半数患病者通常不会有自觉患病，患者在感染两周后开始起皮疹，约维持三天；皮疹往往从脸上开始，蔓延至身体其他部位。皮疹不像麻疹有明显症状，而且有时会痒；通常会伴随淋巴结肿大现象，并且持续数周，发烧、喉咙痛及疲劳也是症状之一，患病的成人也常见关节疼痛。并发症包含出血问题，睾丸肿胀以及神经发炎。怀孕初期患病可能导致婴儿染有先天性风疹症候群（Congenital rubella syndrome / CRS）或流产。先天性风疹症候群的症状包含眼疾如白内障、听觉障碍、心脏问题与脑部问题；但风疹对怀孕20周后的孕妇患者影响较小。

Rubella, also known as German measles or three-day measles, is an infection caused by the rubella virus. This disease is often mild with half of people not realizing that they are sick. A rash may start around two weeks after exposure and last for three days. It usually starts on the face and spreads to the rest of the body. The rash is not as bright as that of measles and is sometimes itchy. Swollen lymph nodes are common and may last a few weeks. A fever, sore throat, and fatigue may also occur. In adults joint pain is common. Complications may include bleeding problems, testicular swelling, and inflammation of nerves. Infection during early pregnancy may result in a child born with congenital rubella syndrome (CRS) or miscarriage. Symptoms of CRS include problems with the eyes such as cataracts, ears such as deafness, heart, and brain. Problems are rare after the 20th week of pregnancy.