Olive mill wastewater (OMWW), a major by-product of olive oil production, contains high organic loads (100–200 g/L) and phenolic compounds (up to 15 g/L) and has a low pH (4.5–5.5). Over 30 million m3 of OMWW is generated globally each year, creating environmental concerns due to its phytotoxic and antimicrobial properties. Traditional treatments are expensive and often result in the loss of valuable phenolics. Instead, valorization provides a sustainable approach by mitigating pollution while recovering bioactive compounds for diverse applications. OMWW is rich in phenolics like hydroxytyrosol, tyrosol, and oleuropein, known for their antioxidant, antimicrobial, antiparasitic, and UV-absorbing properties. These compounds scavenge free radicals, protect against oxidative stress, and inhibit pathogens, making them valuable in health supplements, cosmetics, and food preservation. Notably, OMWW-derived phenolics have shown efficacy against coccidia parasites and potential as natural sunscreens. Advancements in extraction technologies, such as membrane filtration and adsorption, improve phenolic recovery, supporting a circular economy approach. This strategy reduces OMWW’s environmental impact while generating valuable products. Our review highlights OMWW valorization as a pathway to eco-friendly innovations in health, agriculture, and cosmetics, promoting both environmental and economic sustainability.