In an intensifying effort to track ocean change and distinguish between natural and anthropogenic drivers, sustained ocean time series measurements are becoming increasingly important. Advancements in the ocean carbon observation network over the last decade, such as the development and deployment of Moored Autonomous pCO₂ (MAPCO₂) systems, have dramatically improved our ability to characterize ocean climate, sea–air gas exchange, and biogeochemical processes. The MAPCO₂ system provides high-resolution data that can measure interannual, seasonal, and sub-seasonal dynamics and constrain the impact of short-term biogeochemical variability on carbon dioxide (CO₂) flux. Overall uncertainty of the MAPCO₂ using in situ calibrations with certified gas standards and post-deployment standard operating procedures is < 2 μatm for seawater partial pressure of CO₂ (pCO₂) and < 1 μatm for air pCO₂. The MAPCO₂ maintains this level of uncertainty for over 400 days of autonomous operation. MAPCO₂ measurements are consistent with shipboard seawater pCO₂ measurements and GLOBALVIEW-CO2 boundary layer atmospheric values. Here we provide an open-ocean MAPCO₂ data set including over 100 000 individual atmospheric and seawater pCO₂ measurements on 14 surface buoys from 2004 through 2011 and a description of the methods and data quality control involved. The climate-quality data provided by the MAPCO₂ have allowed for the establishment of open-ocean observatories to track surface ocean pCO₂ changes around the globe. Data are available at doi:10.3334/CDIAC/OTG.TSM_NDP092 and http://cdiac.ornl.gov/oceans/Moorings/ndp092.