The Reykjavík Marathon is an annual marathon set in Reykjavík, Iceland, held to coincide with the city's Cultural Night Festival in mid-August. It has taken place every year since 1984 and nowadays attracts more than 10,000 participants from around the world. Along with the full marathon, a half marathon and several races of shorter distances are arranged. 

The course of the Reykjavik Marathon is unique, and very scenic. The race starts and finishes downtown within sight of the pond and the city hall. The location is unbeatable, considering that a large number of hotels are within 5 to 10 minutes walking distance from the start of the race. Although only around 200,000 people live in the larger Reykjavik area, large crowds gather in the streets to support the runners. However, parts of the course pass through uninhabited areas where there are few spectators, instead giving the runners a chance to enjoy Iceland's natural environment and the spectacular scenery. The marathon passes through downtown Reykjavik, a residential area, near a salmon river, and along the beach.

The first part of the course runs through a residential area where many of the inhabitants come out of their houses to cheer the runners on. This is followed by a section where the runners pass along the seaside and have excellent views of the ocean, but also of the mountains surrounding Reykjavik, including Esjan and the Snæfellsjökull glacier. Participants in the marathon also run through the Elliðaárdal valley, the location of one of the country’s more popular salmon-fishing rivers, a small waterfall, and some woodland. In the last part of the race, the participants pass a number of famous buildings, including Höfdi House, a Reykjavik City Council reception venue where US President Ronald Reagan and USSR General Secretary Mikhail Gorbachev met for a summit in 1986.