In recent decades, macroalgae have captured the attention of researchers as a source of multiple compounds with applications in the food, pharmaceutical, and cosmetic industries. Compared to terrestrial crops, the production of algal biomass for food-related applications has been proven to be more sustainable, as it can be done without using potable water and arable land while providing relatively high productivity when produced in large-scale seaweed farms. Despite the wide array of advantages of this biomass and its compounds, this biomass is currently under-utilized. The exploitation of selected macroalgae as a source of polyphenolic compounds and/or phlorotannins (i.e. produced mainly by brown seaweeds) still remains in its infancy, although these molecules have attracted the attention of researchers and industry alike due to their wide range of health benefits and possibilities for industrial use. The exploitation of macroalgal polyphenols still faces great challenges at multiple processing stages, including extraction, purification, and characterization. This chapter briefly summarizes the type of polyphenols described in different macroalgal species and the status of the current methods available for their extraction, purification, and characterization. The main challenges of all these processing steps will be discussed and the most promising strategies currently being explored to overcome these bottlenecks for the industrial exploitation of polyphenols. Moreover, the possibilities of the use of these compounds and their main applications in various industries will also be discussed, providing insights into the future direction of the research, market, and prospects of the industrial exploitation of macroalgae as a source of polyphenols.