In the last decades, the maritime sector has experienced significant evolution, thanks to the advancements in autonomous systems that enable innovative functionalities in the domains of scientific, commercial, search and rescue, and defense operations. These kind of systems leverage a broad range of technologies, such as sensor integration, advanced perception, navigation, guidance, and machine learning, providing support to autonomous surface and underwater vehicles for handling dynamic and unpredictable marine environments. Autonomous marine platforms are integral to scientific research, allowing for continuous ocean monitoring, underwater inspections, and environmental data collection. In commercial and industrial scenarios, these systems can optimize shipping efficiency by reducing fuel consumption and improving safety. The defense sector also benefits from autonomous maritime systems in surveillance, counter-mine, and security operations, while search and rescue missions take advantage of autonomous vehicles for rapid response and disaster management. This chapter explores the technologies that enable these systems, their applications in the aforementioned fields, and lastly future developments in maritime autonomy, highlighting their transformative impact and ongoing research efforts to improve their functionalities.