By one measure, this is true. Bill Gates had been the richest man ever, with a fortune that topped $100 billion in 1999. So in simple dollar terms, Bezos is now richer. And while some say Vladamir Putin is probably richer, we have no way of knowing since his wealth is kept secret.
But wealth is all relative. In inflation-adjusted terms, and as a share of a national economy, Bezos still has a ways to go to be the richest man in history.
Let's start with Gates' fortune. In 1999, he became the first person to have 11 zeros. But $100 billion isn't what it used to be. If you adjust for inflation, Gate's $100 billion fortune in 1999 would be worth about $147 billion today. So in inflation-adjusted terms, Bezos is still about $42 billion short of passing Gates.
John D. Rockefeller is often called the richest American ever, since he was the first billionaire. His fortune was estimated at $1.5 billion in 1918, which in inflation-adjusted terms would be about $24 billion today.
That doesn't sound like much. But relative to the economy, $1.5 billion meant a lot more in 1918.
Aside from adjusting for inflation, fortunes can also be measured as a share of national GDP. And by that measure, Rockefeller's fortune was the equivalent of nearly 2 percent of total U.S. economic output at the time. To have the same share today, with a U.S. GDP of over $18 trillion, Bezos would need to be worth over $350 billion.
Historians often say that Augustus Caesar was the richest in relative economic terms, since he ran an empire that accounted for more than a quarter of the global economy at the time. And some say Caesar's fortune was equal to about 20 percent of his empire's economy. That would be the equivalent of nearly $5 trillion today.
So Bezos is the richest in pure dollar terms. But while Amazon may be out to rule the world, Bezos still has trillions to go before he can truly claim to have conquered history's rich list.