金琥（学名：Echinocactus grusonii），又称象牙球、金琥仙人球，是强刺球类仙人掌的代表，原产墨西哥中部圣路易波托西至伊达尔戈干燥炎热的沙漠地带。金琥虽然在观赏植物市场中很普遍，但野生的金琥却是濒危的稀有植物。

本种是仙人掌类中最具魅力的一类植物。它拥有浑圆碧绿的球体及钢硬的金黄色硬刺。球体的直径可达1米左右，球体顶部密生一圈金黄色的绒毛。金琥顶部有21-27个棱脊高耸的直棱(一般仙人球只有棱12-14个)。棱上整齐地排列着较大的刺座。在刺座上密生金黄色辐射状刺8-l0枚，强硬稍弯的金黄色中刺3-4枚。据有关数据，金琥的寿命很长，可活上百年。

成年植物每年4-11月之间从球体顶部绵毛丛中绽放出金黄色或粉红色的钟形大花；花后结毛绒绒的果实。

金琥的栽培变种有：

Echinocactus grusonii, popularly known as the golden barrel cactus, golden ball or, amusingly, mother-in-law's cushion, is a well known species of cactus, and is endemic to east-central Mexico.

It is rare and endangered in the wild, where it is found near Mesa de Léon in the state of Querétaro, and in the state of Hidalgo. The population was critically reduced in the 1990s, by the creation of the Zimapán Dam and reservoir in Hidalgo. The cactus grows in volcanic rock on slopes, at altitudes around 1,400 metres (4,600 ft).