Abstract. One of the most popular investment anecdotes relates how Isaac Newton, after cashing in some large early gains, staked his fortune on the suc- cess of the South Sea Company of 1720 and lost heavily in the ensuing crash. However, this tale is based on only a few scraps of hard evidence, some of which are consistently misquoted and misinterpreted. Much of what has been published is embellished with questionable flourishes. A superficially plausible argument has also been made that he did not lose much in that period, and John Maynard Keynes even claimed Newton successully surmounted the South Sea Bubble. This paper presents extensive new evidence that while Newton was a successful investor before this event, the folk tale about his making large gains but then being drawn back into that mania and suffering large losses is almost certainly correct. It probably even understates the extent of his financial miscal- culations. Incidentally to the clarification of this prominent issue, a controversy between Dale et al. and Shea about an aspect of market rationality during that bubble is settled. Some new information is also presented about Thomas Guy, famous for making a fortune out of the Bubble that paid for the establishment of Guy’s Hospital, and other investors. The work reported here suggests new research directions and perspectives on bubbles.