The longest bone in the human body is the femur, commonly known as the thigh bone. It extends from the hip to the knee and plays a critical role in supporting the body's weight, allowing for movement and stability during various activities such as walking, running, and jumping. The femur is not only the longest bone but also one of the strongest, designed to withstand significant forces during dynamic activities. The average length of the femur varies among individuals but generally ranges from about 18 to 20 inches in adults. Its structure is essential for bipedal locomotion.