Celebrity is a condition of fame and broad public recognition of a person or group due to the attention given to them by mass media. The word is also used to refer to famous individuals. A person may attain celebrity status by having great wealth, participation in sports or the entertainment industry, their position as a political figure, or even their connection to another celebrity. 'Celebrity' usually implies a favorable public image, as opposed to the neutrals 'famous' or 'notable', or the negatives 'infamous' and 'notorious'.

In his 2020 book Dead Famous: An Unexpected History Of Celebrity, British historian Greg Jenner uses the definition:

Celebrity (noun): a unique persona made widely known to the public via media coverage, and whose life is publicly consumed as dramatic entertainment, and whose commercial brand is made profitable for those who exploit their popularity, and perhaps also for themselves.

Although his book is subtitled "from Bronze Age to Silver Screen", and despite the fact that "Until very recently, sociologists argued that celebrity was invented just over 100 years ago, in the flickering glimmer of early Hollywood" and the suggestion that some medieval saints might qualify, Jenner asserts that the earliest celebrities lived in the early 1700s, his first example being Henry Sacheverell. Over time, the invention of more types of mass media has broadened the ways in which people have become famous.

Athletes in Ancient Greece were welcomed home as heroes, had songs and poems written in their honor, and received free food and gifts from those seeking celebrity endorsement. Ancient Rome similarly lauded actors and notorious gladiators, and Julius Caesar appeared on a coin in his own lifetime (a departure from the usual depiction of battles and divine lineage).

In the early 12th century, Thomas Becket became famous following his murder, the first possible case of posthumous popularity. The Christian Church promoted him as a martyr, and images of him and scenes from his life became widespread in just a few years. In a pattern often repeated, what started as an explosion of popularity (often referred to with the suffix 'mania') turned into long-lasting fame: pilgrimages to Canterbury Cathedral, where he was killed, became instantly fashionable, and the fascination with his life and death inspired plays and films.

The cult of personality (particularly in the west) can be traced back to the Romantics in the 18th century, whose livelihood as artists and poets depended on the currency of their reputation. Lord Byron became a celebrity in 1812 after the publication of the first two cantos of Childe Harold's Pilgrimage. "I awoke one morning and found myself famous," he said. According to McGann: "He rapidly became the most brilliant star in the dazzling world of Regency London."

Establishing cultural hot spots became important in generating fame, such as in London and Paris in the 18th and 19th centuries. Newspapers started including "gossip" columns, and certain clubs and events became places to be seen to receive publicity. Madame Tussauds, a museum that displays waxworks of famous figures, was first established in Baker Street, London in 1835, with Punch in 1849 stating: "In these days, no one can be considered positively popular, unless he is admitted into the company of Madame Tussaud's celebrities in Baker Street". David Lodge called Charles Dickens the "first writer to feel the intense pressure of being simultaneously an artist and an object of unrelenting public interest and adulation", and Juliet John backed up the claim for Dickens "to be called the first self-made global media star of the age of mass culture."