How many years can a goldfish last for?

Fancy goldfish (the ones with a rounder body and double tail) live for around 5-10 years depending on breeding and water quality. Common goldfish (with the more streamlined body and single tail) can live for around 20 years. Goldfish very rarely reach this age because people keep them in tanks and bowls that are too small. It is a myth that they grow to the size of their tank, this causes stunting which shortens their life-span considerably.
Well cared for, and in the right tank size, the life span of a goldfish can be 20+ years