金鱼（学名：Carassius auratus auratus）是一种原产于中国的观赏鱼类，是野生鲫鱼演化而来的彩色变种。

野生鱼类中自然有些色彩鲜艳的鱼，不仅是鲫鱼还有红鲤鱼等。彩色鲫鱼遗传性状比较稳定，中国的金鱼主要是在鲫鱼上发展而来。而彩色鲤鱼传到日本后得到很大重视。

早在两千年前的古书《山海经》中就有红色鲫鱼的记载，“睢水出焉，东南流注于江，其中多丹粟，多文鱼。”郭璞说「文鱼」是“有斑采也”。因为变色的鲫鱼在自然界中太明显，很容易被天敌捕捉。汉宣帝时王褒有《九怀赋》中说：“蛟龙兮导引，文鱼兮上濑。”

The goldfish (Carassius auratus) is a freshwater fish in the family Cyprinidae of order Cypriniformes. It was one of the earliest fish to be domesticated, and is one of the most commonly kept aquarium fish.

A relatively small member of the carp family (which also includes the koi carp and the crucian carp), the goldfish is a domesticated version of a less-colourful carp (Carassius auratus) native to east Asia. It was first domesticated in China more than a thousand years ago, and several distinct breeds have since been developed. Goldfish breeds vary greatly in size, body shape, fin configuration and colouration (various combinations of white, yellow, orange, red, brown, and black are known).