Sunscreen, also known as sunblock or sun cream, is a photoprotective topical product for the skin that helps protect against sunburn and most importantly prevent skin cancer. Sunscreens come as lotions, sprays, gels, foams (such as an expanded foam lotion or whipped lotion ), sticks, powders and other topical products. Sunscreens are common supplements to clothing, particularly sunglasses, sunhats and special sun protective clothing, and other forms of photoprotection (such as umbrellas).

Sunscreens are classified into two types: mineral (also referred to as physical) sunscreens (i.e., zinc oxide and titanium dioxide) and chemical (also referred to as petrochemical, as they are typically derived from petroleum) sunscreens. Research by the FDA on the safety of the main three organic UV filters (oxybenzone, homosalate and octocrylene) found that the three ingredients could be detected on the skin, in blood, in breast milk and in urine samples weeks after no longer being used.

Medical organizations such as the American Cancer Society recommend the use of sunscreen because it aids in the prevention of squamous cell carcinomas. The routine use of sunscreens may also reduce the risk of melanoma. However, many sunscreens do not block ultraviolet A (UVA) radiation, yet protection from UVA is important for the prevention of skin cancer.

To provide a better indication of their ability to protect against skin cancer and other diseases associated with UVA radiation (such as phytophotodermatitis), the use of broad-spectrum (UVA/UVB) sunscreens has been recommended. Some sunscreens include an expiration date—a date indicating when they may become less effective.