古戈尔（英语：googol），又译估勾儿、古高尔，指自然数10，用电子计算器显示是1e100，即数字1后挂100个0。这个单词是在1938年美国数学家爱德华·卡斯纳（Edward Kasner）九岁的侄子米尔顿·西罗蒂（Milton Sirotta）所创造出来的。卡斯纳在他的《数学与想象》（Mathematics and the Imagination）一书中写下了这一概念。

古戈尔是个很大的自然数，它是一个有200个质因子的合数，这些质因子分别是100个2和100个5，它的数量级和70的阶乘（70!）相同。因 ，在二进制里，它占据333个比特（约合42字节）大小。

A googol is the large number 10. In decimal notation, it is written as the digit 1 followed by one hundred 0s:

The term was coined in 1920 by 9-year-old Milton Sirotta (1911–1981), nephew of American mathematician Edward Kasner. Kasner popularized the concept in his 1940 book Mathematics and the Imagination. Other names for googol include ten duotrigintillion on the short scale, ten thousand sexdecillion on the long scale, or ten sexdecilliard on the Peletier long scale.