For some, football is just a game. But for others, a match against their arch-rivals means a clash of identities, political or even religious beliefs. It arouses so much passion that some games end in violence. Young Post looks at five of the most intense rivalries in the world of football and the history behind them.
5. AS Roma vs SS Lazio, Italy
Kicking off the list is a feud in the Italian capital of Rome, and its origins can be traced back to before the second world war.
In 1927, three of the four main football clubs in Rome merged: Roman, Alba-Audace and Fortitudo, to form AS Roma. The purpose of the merger was to give the capital a team strong enough to challenge the dominance of clubs based in northern Italy, such as Juventus. SS Lazio was the only team to resist the merger, and thus a rivalry between the two teams was born.
These days, when Roma and Lazio clash, the police are put on high alert because fans of the losing team often riot in the streets of Rome.
4. Liverpool vs Manchester United, England
The North West Derby pits Liverpool and Manchester United, two of the most successful clubs in the world, against each other in a fierce contest.
The rivalry was originally economic. Before the Industrial Revolution, the port of Liverpool enjoyed economic success through its shipping industry.
But in 1894, once the Manchester Ship Canal was built, ships could sail directly into Manchester. This practically destroyed Liverpool's shipping industry and crippled its economy. So Liverpudlians took their resentment of Manchester to the football pitch.
Today, when Liverpool meet Manchester United, fans of both sides taunt and mock each other, with fights occasionally breaking out.
3. Barcelona vs Real Madrid, Spain
Any time Barcelona and Real Madrid meet, it's called "El Clásico". The last El Clásico, in May, attracted more than 500 million viewers worldwide, making it the most-watched fixture in the world.
The rivalry finds it roots in the fact that Madrid and Barcelona are the two largest cities in Spain. The two cities are often associated with having opposite political views, dividing on the subject of Catalonian and Spanish identity. Lots of people in Barcelona, the largest city in Catalonia, support Catalan nationalism, or the idea that Catalonia should be independent from the rest of Spain.
Catalonians have developed a bitter hatred for Spain's capital Madrid, which is associated with supporting Spanish nationalism, or the idea that Spain should remain a unified country. Real Madrid is the strongest of all the Spanish clubs and Barcelona is Catalonia's champion, so they carry their political rivalry on to the football pitch.
2. Celtic vs Rangers, Scotland
Celtic and Rangers are both based in Glasgow, Scotland, and when they play against each other, the match is referred to as an "Old Firm" game.
Historically, Celtic fans were Catholics while Rangers fans were Protestants.
Since Henry VIII separated the Church of England from the Roman Catholic Church in the 16th century, Catholics and Protestants have had different interpretations of the Bible. This has caused a long-running religious divide in the city, and it's most evident on the football pitch.
Fans sing songs, wave banners and make gestures that insult their opposite number. An activist group reported that on Old Firm weekends, violent attacks increase by nine times in Glasgow, and on-pitch battles are not uncommon.
1. Boca Juniors vs River Plate, Argentina
Fans call this the "Superclásico". This can be seen as a battle between the upper and the lower class in Buenos Aires.
Initially, both Boca Juniors and River Plate originated at the docks of Argentina's capital, Buenos Aires.
In 1925, River Plate moved to Núñez, a wealthy neighbourhood north of the city. Since then, Boca has been considered the "people's club" while River Plate have earned the nickname of "the millionaires".
The rivalry is so great that after a match in May this year, four River Plate players had to be admitted to hospital after being repeatedly hit with pepper spray by Boca Juniors fans. At most matches, some 1,200 police officers are present to control the fans.