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The iliopsoas musculotendinous unit (IPMU), composed of the psoas major, psoas minor, and iliacus muscles, functions as the primary flexor of the thigh and contributes to external rotation and stabilization of the hip and lumbar spine (see Image. Right Hip and Femoral Muscles, Anterior View). The psoas major originates from the lumbar vertebrae, while the iliacus arises from the iliac fossa. Both insert onto the lesser trochanter. Blood supply derives primarily from branches of the external iliac and lumbar arteries, with venous drainage to the external iliac vein. Innervation arises from the lumbar plexus, with contributions from L1 to L3 to the psoas muscles and the femoral nerve (L2–L4) to the iliacus. Notable variants include absence of the psoas minor, accessory muscular slips, and bifid or multiple tendinous insertions. The IPMU has clinical significance due to its proximity to abdominal and pelvic viscera, variable anatomy, and susceptibility to conditions such as tendinopathy, bursitis, hematoma, abscess, and snapping hip, which may mimic intra-abdominal or neuropathic pathology. Within surgical contexts, operations involving the hip and retroperitoneum may present complications, including tendon impingement following arthroplasty, abscess requiring drainage, or contracture requiring tenotomy. Knowledge of iliopsoas anatomy and function enables accurate diagnosis of hip and groin pain, guides appropriate imaging and management strategies, and helps prevent iatrogenic injury during surgical and interventional procedures.