Portrait of Catherine II, also known as Catherine the Great (Stettin, 1729-Pushkin, 1796), Empress consort of Peter III of Russia (1728-1762), painting by Fyodor Rokotov (1735 or 1736-1808), ca 1770
Polish by birth, Catherine the Great assumed power in Russia when her husband Peter III was assassinated in 1762.
Fyodor Rokotov/DEA/A. Dagli Orti—Getty Images/DeAgostini

Historically, women have had a tough time getting rich.

Everything from male primogeniture rules to laws preventing women from holding property have limited the number of female tycoons through the ages. The few that did amass large fortunes typically inherited them from men in their family. "Women with huge personal wealth are a modern phenomenon," says Walter Scheidel, a professor of ancient history at Stanford University.

Which is why, when Money compiled a ranking of the 10 richest people in history last year, the list featured only men. That ranking was challenging in its own way—comparing the wealth of individuals across different eras and geographies in an apples-to-apples way isn't easy—so Money borrowed a technique developed by the historians and economists at MeasuringWorth, which compares an individual's wealth to total global economic output at the time.

We have followed the same methodology for this new list, but in addition, we've chosen to focus on only those women who went beyond just inheritance and took an active business or political role in managing their fortunes, even if they originally acquired them from fathers or husbands. So you won't find women like Walmart widow Christy Walton and heiress Alice Walton, who have never had a hand in the day-to-day operations of the company. (The latter, with a net worth of $32.4 billion, tops the list of America's richest women.)

You also won't see wealthy royals like English monarchs Victoria and Elizabeth I on the list, or Egyptian queen Nefertiti. While each controlled power and money aplenty, none held a sufficient share of the world's riches to make the cut. Similarly, in modern times, billionaire business tycoons like Oprah Winfrey and Theranos founder Elizabeth Holmes—with fortunes of $3 billion and $4.5 billion, respectively—aren't flush enough relative to global GDP to be included. (Historic GDP data comes from the Maddison Project.)

To compile our list, we consulted nearly 30 historians and researched dozens of likely candidates. What follows is a meticulous—if debatable—ranking of the wealthiest women in history.

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Additional reporting by Sophia Tewa and Rebecca Sesny