Cholecalciferol, also known as vitamin D3, colecalciferol or calciol, is a skin-made vitamin D that is found in certain foods and used as a dietary supplement. It was first described in 1936, and is on the World Health Organization's List of Essential Medicines. In 2023, it was the 68th most commonly prescribed medication in the United States, with more than 9 million prescriptions, and is available as a generic medication.