The famed physicist recognized for his work on the Manhattan Project is J. Robert Oppenheimer. As the project’s scientific director, he played a crucial role in the development of the first nuclear weapons during World War II. Oppenheimer's leadership and expertise in theoretical physics were pivotal in the project’s success, which culminated in the testing of the atomic bomb in 1945. Despite his crucial contributions, he later grappled with the moral implications of nuclear warfare.