A white coat or laboratory coat (abbreviated lab coat) is a knee-length overcoat/smock worn by professionals in the medical field or by those involved in laboratory work to protect their street clothes. The garment is made from white or light-colored cotton, linen, or cotton polyester blend, allowing it to be washed at high temperature and make it easy to see if it is clean. Similar coats are a symbol of learning in Argentina, where they are worn by students. In Tunisia, teachers wear white coats to protect their street clothes from chalk.

When used in the laboratory, they protect against accidental spills, e.g. acids. In this case they have to have long sleeves and be made of an absorbent material, such as cotton, so that the user can be protected from the chemical. Some lab coats have buttons at the end of the sleeves, to secure them around the wrist so that they do not hang into beakers of chemicals. Short-sleeved lab coats also exist, and are favoured by certain scientists, such as microbiologists, to avoid the problem of hanging sleeves altogether, combined with the ease of washing the forearms (an important consideration in microbiology).

Like the word "suit", the phrase "white coat" is sometimes used to denote the wearer, i.e. the scientific personnel in a biotechnology or chemical company.