Lactate, with a chemical formula of C₃H₆O₃, is an intermediate product of glucose metabolism in the body and a raw material for hepatic gluconeogenesis. Under physiological resting conditions, the body mainly relies on aerobic oxidation of sugar and fat for energy supply, so the blood lactate concentration is lower. However, during exercise, the enhanced glycolysis in skeletal muscles leads to the significant release of lactate into the bloodstream, causing a marked increase in blood lactate concentration. Traditionally, lactate has been regarded as a metabolic waste product of glycolysis and a contributor to exercise-induced fatigue. Nevertheless, recent studies have revealed that, in humans, lactate is a major vehicle for carbohydrate carbon distribution and metabolism, serving not only as an energy substance alongside glucose but also as a vital component in various biological pathways involved in cardiac energetics, muscle adaptation, brain function, growth and development, and inflammation therapy. Two primary pathways can elevate lactate levels in neurons during exercise. One is peripheral skeletal muscle-derived lactate, which can enter the bloodstream and cross the blood-brain barrier into the brain with the assistance of monocarboxylate transporters (MCTs) from the solute carrier family 16 (SLC16). The other is the central brain-derived pathway. During exercise, neuronal activity is enhanced, promoting the secretion of neuroactive substances such as glutamate, norepinephrine, and serotonin in the brain. This activates astrocytes to break down glycogen into lactate and stimulates glutamate from the presynaptic terminal into the synaptic cleft. It upregulates the glucose transport protein-1 (GLUT-1) expression, allowing astrocytes to convert glucose into lactate through glycolysis. The lactate is produced via peripheral pathways and central pathways during exercise are transported by astrocyte membrane monocarboxylate transporters MCT1 and MCT4 to the extracellular space, where neurons take it up through neuronal cell membrane MCT2. The lactate in neurons can serve as an alternative energy source of glucose for neuronal functional activities, meeting the increased energy demands of synaptic activity during exercise, and maintaining energy balance and normal physiological function in the brain. Additionally, acting as a signaling molecule lactate can enhance synaptic plasticity through the SIRT1/PGC-1α/FNDC5 and ERK1/2 signaling pathways, lactate can promote angiogenesis by upregulating VEGF-A expression through the PI3K/Akt and ERK1/2 signaling pathways, stimulate neurogenesis via the Akt/PKB signaling pathway, and reduce neuroinflammation through activation of the “lactate timer”. Overall, lactate contributes to the protection of neurons, the promotion of learning and memory, the enhancement of synaptic plasticity, and the reduction of neuroinflammation in the nervous system. While lactate may serve as a potential mediator for information exchange between the peripheral and central nervous systems during exercise, further experimental research is needed to elucidate its action mechanisms in the nervous system. In addition, future studies should utilize advanced neurophysiological and molecular biology techniques to uncover the importance of lactate in maintaining brain function and preventing neurological diseases. Accordingly, this article first reviews the historical research on lactate, then summarizes the metabolic characteristics and neuronal sources of lactate, and finally explores the role and mechanisms of exercise-induced lactate in the nervous system, aiming to provide new perspectives and targets for understanding the mechanisms underlying exercise promotion of brain health.