The femur, also known as the thigh bone, is located in the upper part of the leg. It is the longest and strongest bone in the human body, extending from the hip joint to the knee joint. The femur plays a critical role in supporting the weight of the body during standing, walking, and running, while also providing the necessary structure for the muscle attachments that facilitate movement. A healthy femur is essential for mobility and overall leg function, making it a vital component of the human skeletal system.