The National Science Foundation-funded Ocean Observatories Initiative (OOI) is an integrated infrastructure program composed of science-driven platforms and sensor systems that measure physical, chemical, geological and biological properties and processes from the seafloor to the air-sea interface. The OOI network was designed to address critical science-driven questions that will lead to a better understanding and management of our oceans, enhancing our capabilities to address critical issues such as climate change, ecosystem variability, ocean acidification, and carbon cycling. The OOI has transformed research of the oceans by integrating multiple scales of globally distributed marine observations into one observing system and allowing for that data to be freely downloaded over the internet in near-real time. The OOI will continue to deliver data and data products for a 25-year-plus time period within an expandable architecture that can meet emerging technical advances in ocean science. Building on last century’s era of ship-based expeditions, recent technological leaps have brought us to the brink of a sweeping transformation in our approach to ocean research – the focus on expeditionary science is shifting to a permanent presence in the ocean. As technological advances continue over the lifetime of the OOI, developments in sensors, computational speed, communication bandwidth, Internet resources, miniaturization, genomic analyses, high-definition imaging, robotics, and data assimilation, modeling, and visualization techniques will continue to open new possibilities for remote scientific inquiry and discovery.