Amazon, formed 25 years ago, has eclipsed Microsoft to become the world's most valuable listed company.
The online giant was worth $797bn (£634bn) when the US stock market closed on Monday after rising 3.4% and moved past Microsoft, valued at $789bn.
Jeff Bezos, the founder of Amazon, is the world's wealthiest man, with riches of $135bn, according to Bloomberg's billionaire index.
It is the first time Amazon has held the top position. The share prices of US tech giants have been on a rollercoaster in recent months on worries about sales and trade tensions.
Founded by Mr Bezos in 1994, Amazon started life as a niche second-hand book seller and has become an online retailer of items ranging from fresh food to clothes.
The firm was created in a garage in a suburb of Seattle, Washington.
It was originally called "Cadabra," (as in "abracadabra") and in 1995 sold its first book - Fluid Concepts and Creative Analogies: Computer Models of the Fundamental Mechanisms of Thought, by Douglas Hofstadter.
By early 1996, Amazon was selling books online throughout the US.
The business was floated on the stock exchange in 1997, raising $54m. As a result, Mr Bezos joined the ranks of the world's richest business people before he turned 35 years of age.
For more than a decade, the company put growth ahead of profit, investing in warehouses, distribution networks and data systems.
In 2017, it paid $13.7bn for Whole Foods Market, which brought it a large network of physical stores for the first time.
It has also emerged as a major creator of original entertainment content, producing original drama series.
In addition, it has won the rights to broadcast live sporting action, such as football from England's Premier League and ATP tennis.
The firm has developed a raft of other products and services, including the Kindle e-reader and Alexa virtual assistant, among others.
Major technology stocks have been volatile in recent months. In August, Apple became the world's first public company to be worth $1tn (£767bn), while Amazon achieved that valuation in September.
Since then, Apple's fortunes on the stock market have waned after it warned about a slowdown in China. The tech giant is now valued at $702bn.