Peter Lynch is an American investor best known for managing Fidelity's Magellan Fund from 1977 to 1990, during which the fund's assets grew from $18 million to over $14 billion. His investment approach emphasized thorough research and a focus on companies and industries he understood well, encapsulated in his famous 'invest in what you know' philosophy. Lynch has authored several influential books on investing and remains a respected voice in financial markets.