John C. Bogle was an American investor and philanthropist, best known as the founder of Vanguard Group, one of the largest investment management companies in the world. He pioneered the concept of index investing, which allows investors to buy a broad market index rather than individual stocks, making investing more accessible and cost-effective. Bogle was a strong advocate for low-cost investing and believed in the importance of long-term strategies over short-term speculation. His work has had a significant impact on the investment industry, influencing how millions of people save for retirement and manage their investments.