Fucanases are glycoside hydrolases specifically cleaving glycosidic bonds in sulfated fucans (fucoidans). Primarily sourced from marine bacteria (e.g., Wenyingzhuangia, Formosa), mollusks, and fungi, they are classified into glycoside hydrolase families GH107 and GH168. Biochemical properties vary by source: optimal pH ranges from 5.0–9.1, temperature from 20–60°C, with Ca2+/Mg2+ often acting as activators and Cu2+/Zn2+ as inhibitors. The high specificity of fucanases enables controlled degradation of sulfated fucans into bioactive oligosaccharides with enhanced solubility and diverse therapeutic potentials (e.g., preventing intestinal mucositis/gastric ulcers, improving metabolic inflammation, inhibiting adipogenesis, cosmetic whitening). Fucanases are indispensable tools for structural analysis of sulfated fucans in brown algae and sea cucumbers. While wild-type enzymes face limitations in yield and purification, recombinant expression offers high efficiency, stability, and reduced substrate requirements for structural studies. Current challenges include limited commercial availability and incomplete catalytic mechanism understanding. Future research should focus on discovering novel fucanases and elucidating structure-function relationships to advance their applications in nutraceuticals, pharmaceuticals, and functional materials.