Acyclic terpene derivatives are well known as components of plant essential oils and insect hormones, yet their active biosynthesis also occurs in mammals. The terpenic alcohols—or prenols—geranylgeraniol (GGOH) and farnesol (FOH), together with their prenoic acids and derivatives, were identified in mammalian cells over sixty years ago but remain largely overlooked. These metabolites display diverse biological functions: they induce autophagy, inhibit tumor growth and inflammation, suppress cholesterol synthesis, enhance insulin sensitivity and cognition, regulate sexual characteristics, and promote healthy aging. In mammals, prenols arise from an age-dependent, bidirectional pathway that interconverts polyprenyl diphosphates, prenols, and prenoic acids. They can be oxidized into aldehydes and carboxylic acids or reconverted into diphosphate forms for use in protein prenylation and in the biosynthesis of ubiquinone, cholesterol, and dolichol. While enzymes catalyzing polyprenyl diphosphate dephosphorylation and oxidation steps have been partly characterized, the kinases mediating their reverse phosphorylation remain unidentified. This review summarizes current advances in the understanding of prenol metabolism in mammals, emphasizing its role in metabolic regulation, disease prevention, and longevity. By integrating biochemical and physiological evidence, we highlight the emerging view that these small terpenes constitute a fundamental yet underexplored layer of metabolic control. Greater attention to this pathway may reveal novel strategies for maintaining metabolic health and mitigating age-related disorders.