The femur, or thighbone.
The longest bone in the human body is the femur, also known as the thighbone. It extends from the hip to the knee and constitutes about a quarter of a person’s total height. The femur is not only the longest bone but also the strongest. It is designed to withstand significant stress and pressure, being able to support up to 30 times the weight of an average adult. It plays a crucial role in human locomotion and provides a significant amount of mobility and range of motion.