Prominent American billionaire investors Bill Ackman and David Tepper each significantly increased their holdings of Amazon (AMZN) stock in the first quarter of 2026.According to 13F filings for the first quarter of 2026, Ackman’s Pershing Square allocated approximately 17.4% of its portfolio to Amazon, while Tepper’s Appaloosa allocated approximately 15.2% of its portfolio to Amazon—with Tepper’s holdings nearly doubling quarter-over-quarter.This move came after Amazon reported strong first-quarter results, with the AWS business growing by 28% and annualized revenue from the custom chip business exceeding $20 billion.