A famous hedge fund bought Tesla stock before it surged 91% this year. It potentially raked in over $1.5 billion from the bet.

• Renaissance Technologies potentially made over $1.5 billion in two months after buying Tesla stock last quarter.
• The hedge fund raised its stake to 3.9 million shares, worth about $1.6 billion at the end of December.
• Those shares are now worth almost $3.2 billion after Tesla's 91% stock rally this year.
• If Renaissance bought Tesla at $250 in October and sold at the $97o peak, it could have netted almost $3 billion.
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Renaissance Technologies may have netted over $1.5 billion in two months, as it bought a load of Tesla stock before it rocketed up 91% this year.

The quantitative hedge fund, founded by Cold War codebreaker and math professor Jim Simons, bought 3.3 million shares in Elon Musk's electric-car startup last quarter, recent SEC filings show. The purchases boosted its total holding to about 3.9 million shares - a 2.1% stake - at the end of December, according to Bloomberg data.

Renaissance's Tesla shares were worth about $1.6 billion then, based on Tesla's $418 stock price at the time. Given Tesla's shares now change hands at $800, the fund's stake is now worth almost $3.2 billion.

That return would be remarkable enough, but Simons may have raked in closer to $3 billion if he bought into Tesla at the $250 mark in early October, then sold at the $970 peak earlier this month. At those price points, Renaissance's stake would have surged in value from less than $1 billion to almost $3.8 billion.

Tesla stock skyrocketed after the automaker posted strong earnings, opened its Shanghai factory in record time, and announced a production target of 500,000 vehicles this year. The rally has boosted Tesla's market capitalization to over $140 billion, surpassing the combined market caps of Ford, GM, and Chrysler, the "big three" US automakers.

The stunning stock rally has burned short-sellers and spurred investors, industry veterans, and even politicians to warn it won't last.