Phlorotannins from Fucus vesiculosus, a brown seaweed, are gaining attention for their diverse biological effects, including antioxidant, anti-diabetic, anti-obesity, anticancer, and anti-inflammatory properties. This review analyzes these bioactive compounds, covering their chemical properties, extraction procedures, purification techniques, identification methods, and bioactivity. The review explores various extraction techniques, emphasizing parameter optimization to enhance yield and bioactivity. It then delves into purification processes like liquid-liquid partitioning and size-exclusion chromatography to isolate and concentrate phlorotannins. UHPLC-MS is employed for the identification of the purified phlorotannins, providing information on their molecular weight, structure, and composition. This allows for a deeper understanding of the diverse range of phlorotannins present in Fucus vesiculosus. Phlorotannins are distinguished by their potent antioxidant capabilities and demonstrate significant anti-diabetic and anti-obesity effects. Their potential in combating neurodegenerative diseases, cardiovascular diseases, and cancer highlights their importance in preventing and treating oxidative stress-related and other chronic conditions. Despite promising findings, further research is essential to fully understand their mechanisms and applications in biomedical and industrial fields. This includes exploring their synergistic effects with other bioactive compounds, investigating their long-term safety and efficacy, and developing novel delivery systems for enhanced bioavailability.