This review explores the role of vitamin D (VD3) in the central nervous system (CNS) and its implications for neurological disorders. VD3, synthesized in the skin under sunlight or obtained from diet, is metabolized into calcitriol, the most active form of VD3. It exerts its effects through the vitamin D receptor (VDR), which regulates gene expression. VD3 plays a critical role in brain development, neural function, and protection against aging. It influences the dopaminergic system, neurotrophins, neuroimmunity, and neurotransmission. Research indicates a link between VD3 deficiency and various neurological conditions, including autism, schizophrenia, multiple sclerosis, Parkinson's disease, and Alzheimer's disease. VD3 deficiency during brain development can lead to abnormal CNS development, affecting neural stem cell differentiation, oligodendrocyte maturation, and dopaminergic neuron development. VD3 supplementation has shown potential in alleviating symptoms of these disorders, although results from intervention studies are mixed. The review emphasizes the need for well-designed randomized trials to better understand VD3's therapeutic potential. In schizophrenia, VD3 deficiency is associated with altered dopamine function and increased risk. Clinical trials have shown mixed results, with some showing symptom improvement and others showing no significant effect. In autism spectrum disorder, VD3 supplementation has shown some promise in reducing symptoms, but results are inconsistent. For ADHD, VD3 deficiency is linked to cognitive and behavioral issues, but clinical trials have yielded conflicting results. In Alzheimer's disease, VD3 deficiency is associated with increased risk, and some studies suggest that VD3 supplementation may reduce amyloid-beta accumulation. However, other studies show no significant benefit. In Parkinson's disease, VD3 deficiency is linked to reduced dopamine function, and some studies suggest that VD3 supplementation may slow disease progression. In epilepsy, VD3 deficiency is common, and supplementation has shown some anti-seizure effects. In ALS, VD3 deficiency is associated with worse outcomes, but some studies suggest that VD3 may have protective effects. In headaches and pain, VD3 deficiency is linked to increased risk, and supplementation may help reduce migraine frequency. In sleep disorders, VD3 deficiency is associated with poor sleep quality, and supplementation may improve sleep. In depression and bipolar disorder, VD3 deficiency is linked to mood disorders, and supplementation may help alleviate symptoms. The review highlights the complex role of VD3 in the CNS and its potential therapeutic applications for neurological disorders, emphasizing the need for further research to clarify its mechanisms and efficacy.This review explores the role of vitamin D (VD3) in the central nervous system (CNS) and its implications for neurological disorders. VD3, synthesized in the skin under sunlight or obtained from diet, is metabolized into calcitriol, the most active form of VD3. It exerts its effects through the vitamin D receptor (VDR), which regulates gene expression. VD3 plays a critical role in brain development, neural function, and protection against aging. It influences the dopaminergic system, neurotrophins, neuroimmunity, and neurotransmission. Research indicates a link between VD3 deficiency and various neurological conditions, including autism, schizophrenia, multiple sclerosis, Parkinson's disease, and Alzheimer's disease. VD3 deficiency during brain development can lead to abnormal CNS development, affecting neural stem cell differentiation, oligodendrocyte maturation, and dopaminergic neuron development. VD3 supplementation has shown potential in alleviating symptoms of these disorders, although results from intervention studies are mixed. The review emphasizes the need for well-designed randomized trials to better understand VD3's therapeutic potential. In schizophrenia, VD3 deficiency is associated with altered dopamine function and increased risk. Clinical trials have shown mixed results, with some showing symptom improvement and others showing no significant effect. In autism spectrum disorder, VD3 supplementation has shown some promise in reducing symptoms, but results are inconsistent. For ADHD, VD3 deficiency is linked to cognitive and behavioral issues, but clinical trials have yielded conflicting results. In Alzheimer's disease, VD3 deficiency is associated with increased risk, and some studies suggest that VD3 supplementation may reduce amyloid-beta accumulation. However, other studies show no significant benefit. In Parkinson's disease, VD3 deficiency is linked to reduced dopamine function, and some studies suggest that VD3 supplementation may slow disease progression. In epilepsy, VD3 deficiency is common, and supplementation has shown some anti-seizure effects. In ALS, VD3 deficiency is associated with worse outcomes, but some studies suggest that VD3 may have protective effects. In headaches and pain, VD3 deficiency is linked to increased risk, and supplementation may help reduce migraine frequency. In sleep disorders, VD3 deficiency is associated with poor sleep quality, and supplementation may improve sleep. In depression and bipolar disorder, VD3 deficiency is linked to mood disorders, and supplementation may help alleviate symptoms. The review highlights the complex role of VD3 in the CNS and its potential therapeutic applications for neurological disorders, emphasizing the need for further research to clarify its mechanisms and efficacy.