It could be argued that Surströmming (soured herring) is the foulest of all foods as it is intentionally left to rot. It is a Swedish dish consisting of fermented herring. The cans it is sold in often bulge after prolonged storage, due to the gasses given off during the continued fermentation. When opened, the contents release a strong and sometimes overwhelming odour - as smell is strongly linked to taste the stench may make the food taste worse than it actually is. Because of this pungent odour the dish is often eaten outdoors. According to a Japanese study, a newly opened can of surströmming has one of the most putrid food smells in the world, even more so than similarly fermented fish dishes such as the Hongeohoe (Korea) or Kusaya (Japan).

Durian, also known as king of fruits in Asia, is considered as the foulest smelling food in the world. Some may like it, but some think durian smell likes rotton onions. There are some scientific research trying to identify the substances behind the foul smell, which you can read here.