Hákarl is a typical Icelandic dish, made of fermented shark, mainly Greenlandic shark, which is also called hákarl in Icelandic. Greenlandic shark (Somniosus microcephalus) can reach sizes up to 7 m in length. These sharks are poisonous when fresh due to a high content of uric acid (they have no kidneys to remove the uric acid from the body), but may be consumed after being fermented. During this process the uric acid is destroyed and largely converted into ammonia. The flesh is softened and gets a more jelly-like consistency.

The traditional way of preparing hákarl is to remove all the guts, inner organs, cartilage and head of the shark. The resulting meat is washed and put in a hole in the ground. Preferably in loose gravel or lava sand, which drains the fluids efficiently. The hole is closed and covered with heavy stones to press the meat. Leave for 6-7 weeks (in summer) to 2-3 months (in winter). During this time, fluid will drain from the shark flesh, and the fermentation will progress.

When the fermentation is finished, the meat is soft and smells like ammonia. The meat is recovered and hung to dry on a wooden drying shack. This is a shack or shed with plenty of holes to let the wind in, but enough shade to prevent the sun from shining directly on the shark. The drying time will last between 2 and 4 months. Warm, windy and dry weather will hasten the process, while cold, damp and still weather will delay it. 

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Before use the hákarl is cut in small dice-sized cubes and it is traditionally served with the local sprit, brennivín.

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The modern way of preparing hákarl is to place the shark meat in a perforated plastic container in which the fermentation takes place.

Due to the high ammonia content, many non Icelanders find the taste repulsive, but in Iceland it is considered a delicacy.