A key discovery from the past six decades of solar system exploration is that liquid water oceans may be a common planetary phenomenon. At least six ice-covered moons of the outer solar system present compelling evidence for subsurface oceans, and as such provide highly compelling targets in our search for life beyond Earth, and for the nascent field of comparative oceanography. In this talk I will briefly describe several lines of evidence for these oceans, and then I will detail some of the latest discoveries made about Jupiter’s moon Europa. I will also discuss how the exploration of these worlds can help inform our understanding of the origins of life. I will conclude with an overview of approved, and proposed, missions that will explore these worlds in the coming decades.