<p>Aside from many well-known sources, the greenhouse gas methane (CH<sub>4</sub>) was recently discovered entrapped in sediments of Swiss Alpine glacier forefields derived from calcareous bedrock. A first study performed in one glacial catchment indicated that CH<sub>4</sub> was ubiquitous in sediments and rocks, and was largely of thermogenic origin. Here we present results of a follow-up study, which aimed at (1) determining occurrence and origin of sediment-entrapped CH<sub>4</sub> in other calcareous glacier forefields across Switzerland, and (2) providing an inventory for this sediment-entrapped CH<sub>4</sub>, i.e., determining contents and total mass of CH<sub>4</sub> present, and its spatial distribution within and between five different Swiss glacier forefields situated on calcareous formations of the Helvetic Nappes of the Central Alps.</p> <p> Sediment and bedrock samples were collected at high spatial resolution from the forefields of Im Griess, Griessfirn, Griessen, Wildstrubel, and Tsanfleuron glaciers, representing different geographic and geologic regions of the Helvetic Nappes. We performed geochemical analyses on gas extracted from sediments and rocks, including determination of CH<sub>4</sub> contents, stable carbon-isotope analyses (δ<sup>13</sup>C<sub>CH<sub>4</sub></sub>), and determination of gas-wetness ratios (ratio of CH<sub>4</sub> to ethane and propane contents). To estimate the total mass of CH<sub>4</sub> entrapped in glacier-forefield sediments, the total volume of sediment was determined based on measured forefield area and either literature values of mean sediment depth or direct depth measurements using electrical-resistivity tomography.</p> <p> Methane was found in all sediments (0.08–73.81 μg CH<sub>4</sub> g<sup>−1</sup> dry weight) and most rocks (0.06–108.58 µg CH<sub>4</sub> g<sup>−1</sup>) collected from the five glacier forefields, confirming that entrapped CH<sub>4</sub> is ubiquitous in these calcareous formations. Geochemical analyses further confirmed a thermogenic origin of the entrapped CH<sub>4</sub> (average δ<sup>13</sup>C-CH<sub>4</sub> of sediment: −28.23 (± 3.42) ‰; average gas-wetness ratio: 75.2 (± 48.4)). Whereas sediment-entrapped CH<sub>4</sub> contents varied moderately within individual forefields, we noted a large, significant difference in CH<sub>4</sub> content and total CH<sub>4</sub> mass (range: 200–3881 t CH<sub>4</sub>) between glacier forefields at the regional scale. Lithology and tectonic setting within the Helvetic Nappes appeared to be dominant factors determining rock and sediment CH<sub>4</sub> contents. Overall, a substantial quantity of CH<sub>4</sub> was found to be entrapped in Swiss calcareous glacier forefields. Its potential release and subsequent fate in this environment is the subject of ongoing studies.</p>