Astaxanthin is a ketocarotenoid compound with powerful antioxidant properties and is extracted from a varied group of microorganisms, including microalgae, a diverse multifaceted photosynthetic organism. This pigment possesses great valuable properties like immune-modulating, anticancer, and anti-inflammatory, which enhance its demand in the field medicines, nutraceuticals, and therapies in recent days. Moreover, their utilization in the cosmetic industries, aquaculture, food, and additives make them one of the potent candidates in every sector of applied biology and biotechnology too. A good number of microalgal members, viz. Haematococcus pluvialis, Chlorococcum spp., Chlorella zofingiensis, have already been reported and gained considerable attention among the researchers for their high-valued astaxanthin (ASX). This chapter therefore provides a comprehensive insight into the extraction of ASX from microalgae, its roles in different applied sectors as an innovative green biotechnological tool to enhance its value in the field of bioprospection looking ahead for a secure, wealthy, and sustainable future of mankind.