The Karaiskakis Stadium disaster was an incident that occurred on 8 February 1981 in the Karaiskakis Stadium in Neo Faliro, Piraeus, Greece, after the conclusion of a football match between Olympiacos and AEK Athens. It is the biggest football tragedy in Greece's history, and among the worst in sports history.

A total number of 21 people, 20 supporters of Olympiacos and 1 supporter of AEK, lost their lives while rushing out of the stadium to celebrate the victory of Olympiacos against AEK Athens (60). The accident occurred in the historic Gate 7 ( 7). The stadium has since been rebuilt as a modern football field (not a stadium).

There are still debates regarding the causes that led to the disaster. The main cause of the accident, according to the official police report, seems to have been a partially closed door. While exiting, some fans lost their balance and fell on the last steps. Dozens fell onto each other and were stepped over by a horde of unsuspecting fans who kept coming, making it for most of them extremely difficult to stand up or even defend themselves somehow. 19 supporters lost their lives within the stadium, while another two died of their wounds in hospital. At least 55 more were injured, many of them with major injuries. Most of the dead and wounded were teenagers and young adults.The accident occurred in the Gate 7 of the stadium, the gate where supporters of Olympiacos were concentrated, however, one of the victims was reported to be a supporter of AEK Athens FC friend with an Olympiacos supporter.

In memory of this event, every year on February 8, there is a memorial service at the stadium in honor of the supporters that died in that incident. The service is attended by thousands of fans every year, who are rhythmically shouting the phrase ", , ." (Adhrfia, zte, ess mas odhiyte, "Brothers, you live, you are the ones who guide us."). At the tribune part of the stadium where Gate 7 is now, some seats are colored black instead of red, shaping the number "7", whereas there is also a monument on the eastern side of the stadium, bearing the names of all 21 supporters killed on that day in the stadium.

Even though this incident affected almost solely the fanbase of Olympiacos, other teams occasionally pay their respects to the people killed as well, as they consider the incident to be a tragedy not only for one team but for the whole country. In the past, even foreign teams, such as Liverpool F.C. and Red Star Belgrade have honored the incident's victims.

"Gate 7" ( 7), ne of the biggest and most supportive fan clubs of Olympiacos, was named after the incident. Although "Gate 7" members are generally considered to be ultras, the people sitting in that gate before and during the incident were normal supporters, without season tickets (as in the old stadium only gate 1 - which was a VIP gate - supported some season tickets).

Association football, more commonly known as simply football or soccer, is a team sport played with a spherical ball between two teams of 11 players. It is played by approximately 250 million players in over 200 countries and dependencies, making it the world's most popular sport. The game is played on a rectangular field called a pitch with a goal at each end. The objective of the game is to score more goals than the opposition by moving the ball beyond the goal line into the opposing goal, usually within a time frame of 90 or more minutes.

Football is played in accordance with a set of rules known as the Laws of the Game. The ball is 68–70 cm (27–28 in) in circumference and known as the football. The two teams compete to get the ball into the other team's goal (between the posts and under the bar), thereby scoring a goal. Players are not allowed to touch the ball with hands or arms while it is in play, except for the goalkeepers within the penalty area. Players may use any other part of their body to strike or pass the ball and mainly use their feet. The team that has scored more goals at the end of the game is the winner; if both teams have scored an equal number of goals, either a draw is declared or the game goes into extra time or a penalty shootout, depending on the format of the competition. Each team is led by a captain who has only one official responsibility as mandated by the Laws of the Game: to represent their team in the coin toss before kick-off or penalty kicks.Football is governed internationally by the International Federation of Association Football (FIFA; French: Fédération Internationale de Football Association), which organises World Cups for men and women every four years. The men's FIFA World Cup has taken place every four years since 1930, with the exception of 1942 and 1946 tournaments, which were cancelled due to World War II. Approximately 190–200 national teams compete in qualifying tournaments within the scope of continental confederations for a place in the finals. The finals tournament is held every four years and involves 32 national teams competing over four weeks. It is the most prestigious men's football tournament in the world, and the most widely viewed and followed sporting event in the world, exceeding the Olympic Games. Similarly, the FIFA Women's World Cup has been played every four years since 1991, though football has been played by women since it has existed. A record-breaking 1.12 billion viewers watched the 2019 FIFA Women's World Cup in France.The most prestigious competitions in European club football are the UEFA Champions League and UEFA Women's Champions League, which attract an extensive television audience throughout the world. The final of the men's tournament has been, in recent years, the most-watched annual sporting event in the world. The top five European men's leagues are the Premier League (England), La Liga (Spain), Bundesliga (Germany), Serie A (Italy), and Ligue 1 (France). Attracting most of the world's best players, each of the leagues has a total wage cost in excess of £600 million/€763 million/US$1.185 billion.