Amazon boss Jeff Bezos has sold $US 3 billion ($A4.2 billion) worth of shares in the online retailer this week, according to documents filed with the US Securities and Exchange Commission (SEC).

Bezos has already cashed in Amazon shares worth more than $US10 billion ($A14 billion) this year, according to the SEC.

The 56-year-old founded Amazon in 1994 and is still the largest single shareholder of the company.

With an estimated wealth of around $US190 billion ($A265 billion), Bezos is the richest person in the world, according to Forbes and Bloomberg Billionaires.

Amazon was recently valued at $US1.6 trillion ($A2.2 trillion).

Since the beginning of the year, its share price has risen by more than 75 per cent.