A cigarette is a narrow cylinder containing a combustible material, typically tobacco, that is rolled into thin paper for smoking. The cigarette is ignited at one end, causing it to smolder; the resulting smoke is orally inhaled via the opposite end. Cigarette smoking is the most common method of tobacco consumption. The term cigarette, as commonly used, refers to a tobacco cigarette, but the word is sometimes used to refer to other substances, such as a cannabis cigarette or an herbal cigarette. A cigarette is distinguished from a cigar by its usually smaller size, use of processed leaf, and paper wrapping, which is typically white.

Since the 1920s, scientists and doctors have been able to link smoking with respiratory illness. Researchers have identified negative health effects from smoking cigarettes such as cancer, chronic obstructive pulmonary disease (COPD), heart disease, and other health problems relating to nearly every organ of the body. Nicotine, the psychoactive drug in tobacco, makes cigarettes highly addictive. About half of cigarette smokers die of tobacco-related disease and lose on average 14 years of life. Every year, tobacco cigarettes kill more than 8 million people worldwide; with 1.2 million of those being non-smokers dying as the result of exposure to second-hand smoke. Second-hand smoke from cigarettes causes many of the same health problems as smoking, including cancer, which has led to legislation and policy that has prohibited smoking in many workplaces and public areas. Cigarette smoke contains over 7,000 chemical compounds, including arsenic, formaldehyde, hydrogen cyanide, lead, carbon monoxide, acrolein, and other poisonous substances. Over 70 of these are carcinogenic. Most modern cigarettes are filtered, although this does not make the smoke inhaled from them contain fewer carcinogens and harmful chemicals. Cigarette use by pregnant people has also been shown to cause birth defects, including low birth weight, fetal abnormalities, and premature birth. Smoking rates have generally declined in the developed world, but continue to rise in some developing nations.

Because of their adverse health effects, many countries have strict legislation concerning the marketing and purchasing age of tobacco. Most nations outright ban commercials on cigarettes and have levied taxes on them to dissuade smokers to continue the habit. The first country to introduce a large scale anti-smoking campaign was Nazi Germany and despite its minimal success it did create a blueprint for many other nations to follow.

In the 21st century, a product called an electronic cigarette (also called an e-cigarette or vape) was developed, in which the substance contained within it (typically a liquid solution containing nicotine) is vaporized by a battery-powered heating element, as opposed to being burned. Such devices are commonly promoted by their manufacturers as safer alternatives to conventional cigarettes, although there are some health risks associated with their use. Since e-cigarettes are a relatively new product, scientists do not possess data on their possible long-term health effects.