Background: Vitamin D (VD) deficiency is significantly prevalent in Saudi Arabia, despite the country's plentiful sunlight, and has been increasingly linked to metabolic disorders, particularly type 2 diabetes mellitus (T2DM). This review aims to integrate recent evidence on the clinical ramifications of VD deficiency in Saudi populations, with a focus on diabetes and related metabolic complications. Methods: A comprehensive search of the literature was carried out on PubMed, Scopus, Web of Science, and Google Scholar for studies published from 2010 to 2025. The inclusion criteria encompassed studies that reported VD status in Saudi populations and their associations with diabetes, glycemic control, or cardiometabolic outcomes. Forty-three studies—including observational studies, systematic reviews, and meta-analyses—were included. Data on serum 25-hydroxyvitamin D [25(OH)D], the prevalence of deficiency, metabolic parameters, and clinical outcomes were extracted and synthesized narratively. Results: VD deficiency prevalence has been reported to range from 50% to 85%, affecting children, adolescents, and adults, with women being disproportionately affected. This deficiency was consistently linked to elevated fasting glucose levels, HbA1c, insulin resistance, dyslipidemia, obesity, and an increased risk of cardiovascular issues. The pediatric and adolescent demographics showed signs of impaired bone mineralization and a heightened risk for rickets. Mechanistically, VD deficiency leads to β-cell dysfunction, reduced insulin secretion, peripheral insulin resistance, and systemic inflammation. Some urban areas have seen modest improvements in deficiency rates due to supplementation and awareness initiatives, yet the deficiency remains widespread. Conclusion: Vitamin D deficiency is significantly prevalent in Saudi Arabia and is closely associated with T2DM, cardiometabolic disorders, and skeletal complications. It is advisable to implement routine screening for high-risk groups, targeted supplementation, lifestyle modifications, and public health strategies to alleviate deficiency and its clinical ramifications. Tackling VD deficiency is a clinically actionable strategy to lessen the burden of metabolic and skeletal disorders within Saudi populations.