<p>The quantities of carbon dioxide (CO₂) carried by magmas affect the style of volcanic eruptions and the evolution of Earth’s climate over geological time. There is growing evidence of volatile-rich primary magmas in intraplate domains such as oceanic islands and continental rifts, with CO₂ contents reaching several percent by weight. In most cases, these high CO₂ contents are inferred but not directly measured, because the volcanic products at the surface are strongly degassed. Here, we report the pre-eruptive CO₂ contents measured in olivine-hosted melt inclusions from Bas-Vivarais (Massif Central, France), a typical continental intraplate volcanic province. These basanitic melt inclusions have unusually high CO₂ concentrations of up to 4.8 percent by weight (3.6 percent by weight on average), among the highest ever measured to date. Such CO₂-rich primary magmas appear to be the rule rather than the exception in continental intraplate settings and require carbon-enriched mantle sources (1475 to 2923 parts per million CO₂ for Bas-Vivarais). Despite relatively small magma volumes, eruptions of low-silica alkaline magmas in continental intraplate volcanic provinces release large amounts of CO₂ in the atmosphere. Thus, these provinces contribute much more to the global CO₂ flux and to the Earth’s short-term climate than their low magma production rates would suggest.</p>