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The concentration of carbon in primary mid‐ocean ridge basalts (MORBs), and the associated fluxes of CO₂outgassed at ocean ridges, is examined through new data obtained by secondary ion mass spectrometry (SIMS) on 753 globally distributed MORB glasses. MORB glasses are typically 80–90% degassed of CO₂. We thus use the limited range in CO₂/Ba (81.3 ± 23) and CO₂/Rb (991 ± 129), derived from undegassed MORB and MORB melt inclusions, to estimate primary CO₂concentrations for ridges that have Ba and/or Rb data. When combined with quality‐controlled volatile‐element data from the literature (n = 2,446), these data constrain a range of primary CO₂abundances that vary from 104 ppm to 1.90 wt%. Segment‐scale data reveal a range in MORB magma flux varying by a factor of 440 (from 6.8 × 10⁵to 3.0 × 10⁸m³/year) and an integrated global MORB magma flux of 16.5 ± 1.6 km³/year. When combined with CO₂/Ba and CO₂/Rb‐derived primary magma CO₂abundances, the calculated segment‐scale CO₂fluxes vary by more than 3 orders of magnitude (3.3 × 10⁷to 4.0 × 10¹⁰mol/year) and sum to an integrated global MORB CO₂flux of × 10¹²mol/year. Variations in ridge CO₂fluxes have a muted effect on global climate; however, because the vast majority of CO₂degassed at ridges is dissolved into seawater and enters the marine bicarbonate cycle. MORB degassing would thus only contribute to long‐term variations in climate via degassing directly into the atmosphere in shallow‐water areas or where the ridge system is exposed above sea level.