John Bogle was an American investor and the founder of Vanguard Group, a company known for its low-cost mutual funds. He is credited with popularizing index investing, a strategy that involves buying a broad market index rather than trying to pick individual stocks. This approach allows investors to achieve market returns with lower fees. Bogle's philosophy emphasized the importance of long-term investing and minimizing costs to maximize returns. He authored several books on investing, including The Little Book of Common Sense Investing, which outlines his investment principles. His contributions have had a lasting impact on the investment industry and individual investors alike.