Kidney cancer, also known as renal cancer, is a group of cancers that starts in the kidney. Symptoms may include blood in the urine, lump in the abdomen, or back pain. Fever, weight loss, and tiredness may also occur. Complications can include spread to the lungs or brain.

The main types of kidney cancer are renal cell cancer (RCC), transitional cell cancer (TCC), and Wilms' tumor. RCC makes up approximately 80% of kidney cancers, and TCC accounts for most of the rest. Risk factors for RCC and TCC include smoking, certain pain medications, previous bladder cancer, being overweight, high blood pressure, certain chemicals, and a family history. Risk factors for Wilms' tumor include a family history and certain genetic disorders such as WAGR syndrome. Diagnosis may be suspected based on symptoms, urine testing, and medical imaging. It is confirmed by tissue biopsy.

Treatment may include surgery, radiation therapy, chemotherapy, immunotherapy, and targeted therapy. Kidney cancer newly affected about 403,300 people and resulted in 175,000 deaths globally in 2018. Onset is usually after the age of 45. Males are affected more often than females. The overall five-year survival rate is 75% in the United States, 71% in Canada, 70% in China, and 60% in Europe. For cancers that are confined to the kidney, the five-year survival rate is 93%, if it has spread to the surrounding lymph nodes it is 70%, and if it has spread widely, it is 12%. Kidney cancer has been identified as the 13th most common form of cancer, and is responsible for 2% of the world's cancer cases and deaths. The incidence of kidney cancer has continued to increase since 1930. Renal cancer is more commonly found in populations of urban areas than rural areas.