A bartender (also known as a barkeep or barman or barmaid or a mixologist) is a person who formulates and serves alcoholic or soft drink beverages behind the bar, usually in a licensed establishment as well as in restaurants and nightclubs, but also occasionally at private parties. Bartenders also usually maintain the supplies and inventory for the bar. As well as serving beer and wine, a bartender can generally also mix classic cocktails such as a cosmopolitan, Manhattan, old fashioned, and negroni.

Bartenders are also responsible for confirming that customers meet the legal drinking age requirements before serving them alcoholic beverages. In certain countries, such as the United States, Canada, the United Kingdom, Ireland and Sweden, bartenders are legally required to refuse more alcohol to drunk customers.

Mixology is defined as the art or skill of preparing mixed drinks. At its core, the purpose of this practice is to craft cocktails. However, the science and skills required to successfully practice mixology are more intricate than what is seen at face value. The key to mixing drinks is knowing the ideal quantity of each ingredient needed to create the flavor profile required. Mixology aims to both elevate and balance the various flavors found in a cocktail.

Historically, bartending was a profession with a low reputation. It was perceived through the lens of ethical issues and various legal constraints related to the serving of alcohol.

The pioneers of bartending as a serious profession appeared in the 19th century. Jerry Thomas established the image of the bartender as a creative professional, credited with being the father of American mixology. He earned this title by publishing Jerry Thomas' Bartender's Guide, the first guide to making cocktails in 1862. Thomas perfected his skills by owning and manning saloons across the New York City area throughout the 1800s. Mixology started to take shape in the years following Thomas' book. Harry Johnson published Harry Johnson's New and Improved Illustrated Bartender's Manual in 1882. Both of these books shared recipes for dozens of unique drinks that combined ingredients people had never thought to combine before. Thomas and Johnson incorporated flavored spirits, liqueurs, and fortified wines to their cocktails, which was a new concept. Mixology took off after these two publications. By the late 1800s, the term mixology was common and widely used.

At the turn of the 20th century, slightly fewer than half the bartenders in London were women, such as Ada Coleman. "Barmaids", as they were called, were usually the daughters of tradesmen or mechanics or, occasionally, young women from the "better-born" classes who had been "thrown upon their own resources" and needed an income. Bartending has often been associated with the struggles of marginalized groups in the workforce, such as African-American women. However, women have sometimes been restricted from bartending. For example, Goesaert v. Cleary, 335 U.S. 464 (1948), was a United States Supreme Court case in which the court upheld a Michigan law which prohibited women from being licensed as a bartender in all cities having a population of 50,000 or more unless their father or husband owned the establishment. The decision was subsequently overruled by Craig v. Boren (1976).

After the rise of the cocktail in the early 20th century, Americans were faced with prohibition laws from the federal government. However, bartending culture remained alive throughout prohibition (1920-1933). Working in underground speakeasies, bartenders continued to provide their patrons with cocktails. Following the suspension of the eighteenth amendment and the release of legal alcohol back into the market, the cocktail era took a dip. People drank less and the Great Depression severely limited the ability of people to buy a drink. Cocktails started to be limited to the rich and famous. The celebrities in Los Angeles took a certain liking to the recipes of the old days. But the general population would no longer mix their drinks. Individualism was crushed, similarly to the food industry. The industry needed a renaissance, and it wasn't until the late 90s that the true re-emergence of the cocktail bar occurred.

The bartending profession was generally a second occupation, used as transitional work for students to gain customer experience or to save money for university fees. The reason for this is because bartenders in tipping countries such as Canada and the United States, can make significant money from their tips. This view of bartending as a career is changing around the world, however, and bartending has become a profession by choice rather than necessity. It includes specialized education—European Bartender School operates in 25 countries.