The Marathon is a classic long-distance foot race; the standard distance is 42.195 km (26 miles, 385 yards) though there is some variation between courses. The awkward distance was fixed for the first time for the 1908 Olympic games in London — as legend has it to ensure a final stretch in front of the Royal Box as well as a starting point at Windsor Castle.

More than 500 marathon races are held annually, most of them as road races, though the distance can also be pursued cross-country. For the vast majority of runners, it is not so much a race as an endurance test; they will be happy just to finish, whatever their time, though many compete with themselves hoping to beat their previous times. For others, it is very much a competitive sport; there are substantial cash prizes for some races and the marathon has been an Olympic event since 1896. By tradition, the medals for the men's marathon are always the final ones to be awarded at the Summer Olympics, with its medal ceremony being incorporated into the closing ceremony. In the 21st century, marathons have a tendency to be dominated by runners from Ethiopia and Kenya, though Japan is also a powerhouse in women's marathons.

The name commemorates the battle of Marathon in 490 BC; the Athenians and some allies soundly defeated a Persian invasion force that had just come off ships near the small town of Marathon. According to legend, an army messenger ran non-stop to Athens with the happy news and dropped dead immediately after delivering it. The length of the race is based on the legend and his most likely route. This may not be entirely accurate since a runner might have taken a shorter but hillier alternate route, and the ancient Greeks had horses so they might not have sent a runner at all.

There are ultramarathon races which cover even longer distances. Perhaps the most challenging footrace of all is the Marathon des Sables (Marathon of the Sands), 250 km (156 miles) across part of the Sahara Desert in Morocco.

There is also a triathlon called Ironman; despite the name, women do compete in this event, and the best of them are faster than most men. It starts with a 4 km swim, then 180 km of cycling and finally running a marathon distance. There are several dozen events a year and an annual Ironman World Championship in Hawaii.

Destinations

Helsinki City Marathon in 2012

Many cities host large and prestigious marathons, each attracting top marathoners and huge crowds of non-professional runners. Climate is a major factor in the choice of dates; in the tropics most events are held in winter, elsewhere in spring or fall. Marathon courses are usually designed to pass by some of the most iconic landmarks of the host city.

There is an every-two-years championship series called the World Marathon Majors which includes an IAAF marathon every two years, the Olympic marathon every four, and six annual city marathons:

• Berlin Marathon (Berlin). This has been held every year since 1974 and attracts nearly 40,000 runners. It has hosted six men's world records and three women's world records on its mostly-flat course. Races are typically run in the fall.  
• Boston Marathon (Boston). This race has been run every year since 1897 on Patriots' Day, the third Sunday in April.  
• Chicago Marathon (Chicago). Run in October. The organizers limit it to 45,000 runners, and you need to book months ahead to be sure of being allowed to compete.  
• London Marathon (London). This is held in October. The men's world record has been broken once here, and the women's six times.  
• New York City Marathon (New York City). This is the world's largest marathon, with over 53,000 finishers in 2019. It is held on the first Sunday of November.  
• Tokyo Marathon (Tokyo). Held in February.  

Other cities with marathons include:

• Amsterdam Marathon (Amsterdam). Usually held in October  
• Barcelona Marathon (Barcelona). Usually held in March  
• Beijing Marathon (Beijing). Usually held in October  
• Dubai Marathon (Dubai). This race normally takes place in January, the coolest month in Dubai. It has some of the largest prizes of any marathon, including a million dollar prize for a new world record. The 2021 event was cancelled due to COVID-19 and the 2022 race postponed to December 10. The 2034 run is scheduled for February 12.  
• Finlandia Marathon (Jyväskylä). Usually held in September. 
• Helsinki City Marathon (Helsinki). Usually held in May.  
• Hong Kong Marathon (Hong Kong). Usually held in January or February. Due to COVID-19, the 2020 event was cancelled, 2021 delayed to October, and 2022 to November.  
• Istanbul Marathon (Eurasia Marathon) (Istanbul). The only marathon in the world where the runners swelter on two continents. Many Istanbul dwellers take the opportunity to walk over the Bosphorus Bridge that gets temporarily closed to vehicular traffic during the marathon (no pedestrians are allowed on the bridge at other times). Usually run in November.  
• Mexico City International Marathon (Maratón Internacional de la Ciudad de México) (Mexico City). First run in 1983, the marathon happens each year in late August or early September.  
• Osaka Marathon (Osaka). Usually held in February.  
• Paavo Nurmi Marathon (Turku). Named after Paavo Nurmi (1897–1973), the "Flying Finn", who won a total of nine gold and three silver medals at three Olympic Games from 1920 to 1928. The race is usually held in August.  
• Paris Marathon (Paris). The world's second largest marathon, run in April.  
• Rome Marathon (Rome). Usually run in March or April.  
• Rotterdam Marathon (Rotterdam). Run in April.  
• Shanghai Marathon (Shanghai). Usually run in November  
• Sydney Marathon (Sydney). Usually run in September  
• Xiamen International Marathon (Xiamen). Usually held in January  

Most of the organizers of marathons belong to the Association of International Marathons and Distance Races (AIMS). Their site has a directory listing an enormous number of races worldwide. The International Amateur Athletics Federation (IAAF) also has a long list. There is also a list on Wikipedia.

Sleep

Many people travel for marathons, so lodging selection is important. For major marathons the influx of visitors can overwhelm local lodging options, so plan to book well in advance. Marathons will typically involve shutting down the roads along the course, so transportation to the starting line on race day can be tricky - if you can book a hotel that is close to public transit or near the starting line your marathon experience is likely to be much less stressful.

Particularly if you aren't an experienced marathoner, expect to feel pretty brutalized after completing the course. Most people won't want to spend hours driving or on a plane immediately after putting their body through twenty-six miles of punishment, so booking a hotel for multiple nights - at least the night before and the night after the marathon - is a plan that you are unlikely to regret.

Stay healthy

According to legend, the first marathon runner dropped dead just after finishing the run. That story may not be accurate, but certainly a marathon puts considerable strain on the body. No-one should attempt the race, or even serious training for it, without first talking to their doctor.

There are two water-related dangers; dehydration is uncomfortable, debilitating and dangerous, quite definitely not good for you. On the other hand excessive consumption of fluids can lead to hyponatraemia, a reduction of sodium levels in the blood that is sometimes fatal for long-distance runners.

Many competitors find it necessary to work out a detailed hydration plan in advance so that they can avoid both dehydration and hyponatraemia on race day. Doing this right requires precise advice tailored to your body; consult a doctor with expertise in sports medicine.

Some marathons are run at high altitudes; for those, altitude sickness is an issue. Anyone should at least give themselves a few days to acclimatize before the race, and adjust their hydration plan since altitude can also cause dehydration. Serious competitors will need to train at altitude, and most of the top Ethiopian and Kenyan runners grew up at high altitude.