Archaea are the “silent and unseen majority of life” with an extraordinary capacity to live in some of the most unfavorable habitats in nature, and continue to exist in regions with extreme features that are inhospitable to most other living organisms. They are prokaryotic and frequently found in environments with high pH, salinity, and temperatures. Asgard, Euryarchaeota, TACK, and DPANN are the four main superphyla that make up the Archaea, one of the three domains of life on Earth. Extremophiles, the first Archaea found, are classified into four major physiological types. These are halophiles, thermophiles, alkaliphiles, and acidophiles. The Archaea domain is the subject of extensive research, particularly for potential biotechnological applications. Archaea play a crucial role in environmental sustainability and human health, particularly through their enzymes, metabolites, and biochemical processes. These are some core characteristics of Archaea enabling biotechnological usage. This chapter aims to provide an overview of the various roles that Archaea have in biotechnological usage, both current and potential. Their classification is based on the industry to which the application is targeted, which includes industrial enzyme and catalysis, energy production, and medical and pharmaceutical applications.