The brainstem (Fig. 2.1) represents a critical neuroanatomical structure that serves as the vital connection between the cerebral cortex, cerebellum, and spinal cord. Comprising three distinct regions—the midbrain (mesencephalon), pons, and medulla oblongata—the brainstem orchestrates essential life-sustaining functions including cardiovascular regulation, respiratory control, and consciousness maintenance. This chapter provides a comprehensive examination of brainstem anatomy, beginning with the midbrain’s role in motor coordination and sensory processing through structures such as the substantia nigra, red nucleus, and superior and inferior colliculi. The pons is explored as a crucial relay center connecting the cerebral cortex with the cerebellum while housing vital respiratory centers and cranial nerve nuclei. The medulla oblongata’s function in autonomic regulation and its housing of critical cardiovascular and respiratory centers are detailed. Special attention is given to the distinctive neurochemical nuclei, including dopaminergic, noradrenergic, serotonergic, and cholinergic systems that modulate widespread brain functions. The chapter also examines major ascending and descending pathways, cranial nerve nuclei organization, and vascular supply patterns. Understanding brainstem anatomy is fundamental for clinical neuroscience, as lesions in this region can result in devastating neurological deficits affecting consciousness, motor control, sensation, and autonomic function.