A congenital disorder, also known as a congenital disease or birth defect, is a condition that is present from birth. Congenital disorders can be inherited or caused by environmental factors. They can be defined as structural or functional anomalies that occur during intrauterine life and can be identified prenatally, at birth, or sometimes may only be detected later in infancy. Congenital disorders can be major or minor, with major structural anomalies accounting for most of the deaths, morbidity, and disability related to congenital anomalies. Some common congenital disorders include Down syndrome, spina bifida, and cystic fibrosis. Approximately 6% of babies worldwide are born with a congenital disorder, resulting in hundreds of thousands of associated deaths. The true number of cases may be much higher because statistics do not often consider terminated pregnancies and stillbirths.

The causes of congenital disorders can be hereditary or result from an action or exposure occurring during pregnancy or at birth, or they may be due to a combination of these factors. A minority of congenital disorders are caused by genetic abnormalities, such as chromosomal abnormalities or single gene defects. Socioeconomic and demographic factors, such as low-income, may also be indirect determinants of congenital disorders, with a higher frequency among resource-constrained families and countries.

It is possible to test for some, but not all, congenital disorders during pregnancy. Other things that can be done to try to prevent congenital disorders include eating a healthy diet with enough vitamins and minerals, taking folic acid supplements before and during pregnancy, avoiding alcohol, smoking, and other drugs, and controlling diabetes.