The Super Bowl is the annual championship game of the National Football League (NFL), the highest level of professional American football in the United States, culminating a season that begins in the late summer of the previous calendar year. This game is held at a pre-selected site, usually a city that hosts an NFL team. The Super Bowl uses Roman numerals to identify each game, rather than the year in which it is held, with Super Bowl I being the 1966 season championship game. The defending champions are the Green Bay Packers who won Super Bowl XLV. On February 5, 2012, the New York Giants and New England Patriots will contest Super Bowl XLVI.
The game was created as part of a merger agreement between the NFL and its then-rival league, the American Football League (AFL). It was agreed that the two leagues' champion teams would play in an AFL–NFL World Championship Game until the merger was to officially begin in 1970. After the merger, each league was redesignated as a "conference", and the game was then played between the conference champions. Currently, the NFC leads the series with 24 wins to 21 wins for the AFC.
The day on which the Super Bowl is played is now considered a de facto American national holiday, called "Super Bowl Sunday". It is the second-largest day for U.S. food consumption, after Thanksgiving Day. In addition, the Super Bowl has frequently been the most watched American television broadcast of the year. Super Bowl XLV played in 2011 became the most watched American television program in history, drawing an average audience of 111 million viewers and taking over the spot held by the previous year's Super Bowl, which itself had taken over the #1 spot held for twenty-eight years by the final episode of M*A*S*H. The Super Bowl is also among the most watched sporting events in the world, mostly due to North American audiences, and is second to Association football's UEFA Champions League final as the most watched annual sporting event worldwide.
Because of its high viewership, commercial airtime during the Super Bowl broadcast is the most expensive of the year because the viewing count of the Super Bowl is an average of 100,000,000 people every year. Due to the high cost of investing in advertising on the Super Bowl, companies regularly develop their most expensive advertisements for this broadcast. As a result, watching and discussing the broadcast's commercials has become a significant aspect of the event. In addition, many popular singers and musicians have performed during the event's pre-game and halftime ceremonies because of the exposure.