An oil lamp is a lamp used to produce light continuously for a period of time using an oil-based fuel source. The use of oil lamps began thousands of years ago and continues to this day, although their use is less common in modern times. They work in the same way as a candle but with fuel that is liquid at room temperature, so that a container for the oil is required. A textile wick drops down into the oil, and is lit at the end, burning the oil as it is drawn up the wick.

Oil lamps are a form of lighting, and were used as an alternative to candles before the use of electric lights. Starting in 1780, the Argand lamp quickly replaced other oil lamps still in their basic ancient form. These in turn were replaced by the kerosene lamp in about 1850. In small towns and rural areas the latter continued in use well into the 20th century, until such areas were finally electrified and light bulbs could be used.

Sources of fuel for oil lamps include a wide variety of plants such as nuts (walnuts, almonds, and kukui) and seeds (sesame, olive, castor, or flax). Also widely used were animal fats (butter, ghee, fish oil, shark liver, whale blubber, or seal). Camphine, a blend of turpentine and ethanol, was the first "burning fluid" fuel for lamps after whale oil supplies were depleted. It was replaced by kerosene after the US Congress enacted excise taxes on alcohol to pay for the American Civil War.

Most modern lamps (such as fueled lanterns) have been replaced by gas-based or petroleum-based fuels to operate when emergency non-electric light is required. Therefore, oil lamps of today are primarily used for the particular ambience they produce.