周围神经系统（英语：Peripheral Nervous System，缩写为PNS），又称外周神经系统、周边神经系统、边缘神经系统或末稍神经系统，是神经系统的组成部分，包括除脑和脊髓之外的神经部分。 脑和脊髓组成中枢神经系统。相比后者，周围神经系统没有骨骼和血脑屏障的保护。周围神经系统又分为躯体神经系统和自主神经系统。

但PNS和CNS的划分并非着眼于其功能。神经元由胞体和其突起组成。运动（专司随意运动）和植物性（内部器官的功能调节）神经元的胞体都在CNS。感觉（传导感觉）神经元的胞体则几乎都在PNS的神经节中，但是它们都有突起传入CNS。信息会在CNS汇总集成，并引发随意或不随意的反应（反射）。所以周围神经系统并非独立，只是一个形态划分。例外是肠神经系统，其信息集成部分独立于CNS。

The peripheral nervous system (PNS) is the part of the nervous system that consists of the nerves and ganglia on the outside of the brain and spinal cord. The main function of the PNS is to connect the central nervous system (CNS) to the limbs and organs, essentially serving as a communication relay going back and forth between the brain and spinal cord with the rest of the body. Unlike the CNS, the PNS is not protected by the bone of spine and skull, or by the blood–brain barrier, which leaves it exposed to toxins and mechanical injuries. The peripheral nervous system is mainly divided into the somatic nervous system and the autonomic nervous system. In the somatic nervous system, the cranial nerves are part of the PNS with the exception of cranial nerve II, the optic nerve, along with the retina. The second cranial nerve is not a true peripheral nerve but a tract of the diencephalon. Cranial nerve ganglia originate in the CNS. However, the remaining ten cranial nerve axons extend beyond the brain and are therefore considered part of the PNS. The Autonomic nervous system is an involuntary control of smooth muscle. The connection between CNS and organs allows the system to be in two different functional states: sympathetic and parasympathetic.