The Orbiting Carbon Observatory 3, or OCO-3, is a future space instrument designed to investigate important questions about the distribution of carbon dioxide on Earth as it relates to growing urban populations and changing patterns of fossil fuel combustion.

NASA plans to develop and assemble the instrument using spare materials from the successful development and launch of the Orbiting Carbon Observatory 2 in 2014 and host the instrument on the International Space Station or another space-based platform.