Amazon cracked the top 10 for the first time, continuing its remarkable growth run.
Apple dropped from last year's No.3 to the fourth place despite a 6 percent gain in annual sales.
This year's Fortune 500 companies represent two-thirds of the US GDP.
Technology companies dominated this year's Fortune 500 list released on Monday, with Apple, Amazon, Alphabet, Microsoft and IBM, among others, all in the top 50.
Apple dropped from last year's No.3 to the fourth place despite a 6 percent gain in annual sales, but it led the way in profits with more than $48 billion (about Sh4.8 trillion) in net income, according to the list.
Amazon cracked the top 10 for the first time, continuing its remarkable growth run: Sales have jumped some $70 billion (about Sh7 trillion) in two years.
Amazon's enormity stems from its role as the largest US digital retailer, the fastest-growing part of the market. Shares of the company rose 0.35 per cent to trade at $1,579.91 (about Sh158,938) a piece in early trading on Monday.
Apple, Alphabet, Microsoft and Amazon were the top four in market value as of March 29 this year, according to the list.
They are followed by Berkshire Hathaway, Facebook and JPMorgan Chase. Fortune ranks the world's top companies by revenue each year and 2018 marks the 64th running of the list.
This year's Fortune 500 companies represent two-thirds of the US GDP with 12.8 trillion dollars in revenues, $1 trillion in profits, $21.6 trillion in market value and employ 28.2 million people worldwide.
Walmart, Exxon Mobil, Berkshire Hathaway, Apple, UnitedHealth Group, McKesson, CVS Health, Amazon, AT&T, and General Motors made the top 10 this year.
Among them, Exxon Mobil and General Motors have been on the list every year since it started in 1955.
