AbstractPeatlands in the northern hemisphere are important stores of soil carbon. The stability of peatlands is therefore important for the preservation of a major terrestrial carbon store as well as for the maintenance of the carbon storage function of peatlands. Peatland erosion has the potential to significantly impact carbon storage. This article reviews the evidence from eroding peatland systems, largely in the United Kingdom, to develop the thesis that as peatlands begin to erode, geomorphological processes and form become the dominant controls on peatland carbon cycling. The impacts of geomorphological change on carbon cycling include direct erosional losses of particulate organic carbon (POC) and indirect effects largely resulting from the effect of gully erosion on peatland water tables, and consequently on dissolved and gaseous carbon losses. During erosional phases, POC loss from eroding systems can be sufficient to shift peatlands from net carbon sinks to net carbon sources. Re‐vegetation of eroding peatlands dramatically reduces POC loss but morphological changes resulting from erosion are likely to cause long‐term changes in gaseous and dissolved carbon flux from re‐vegetated peatlands. The potential for enhanced peatland erosion resulting from climatic changes in peatland areas requires a fuller understanding of geomorphological controls on carbon losses. In particular the fate of POC losses from peatlands is an urgent research need.