Food is an essential component of life for all humans and animals present on this planet, and food security is becoming more challenging across countries due to reduced food production, increased population, and climatic changes. Most of the nations are hastening to increase their food productivity to counteract food scarcity and undernourishment. The agriculture industry is the primary reservoir for food production and aids in reducing hunger, poverty, and food security. Recent trends in the usage of chemical fertilizers, pesticides, and herbicides to enhance crop productivity may provide better yields for shorter duration. Still, in the long run, this causes severe issues in soil fertility and affects soil ecosystems. Sustainable, eco-friendly agricultural practices are the future ventures of agriculture using microbe-based plant growth stimulants, fungicides, and pesticides. The genus Actinobacteria is renowned for its therapeutic and industrial values. However, their agricultural applications are merely overlooked. In addition, actinobacteria from terrestrial and coastal ecosystems have been widely explored, leaving the extreme marine environmental sites untouched. This book chapter focuses on uncovering the functional properties of polyextremophilic marine actinobacteria and their role and mechanism of action in plant growth promotion.