Stomach cancer is the second most frequent cause of cancer-related death worldwide. Thus, it is important to elucidate the properties of gastric stem cells, including their regulation and transformation. To date, such stem cells have not been identified in Drosophila. Here, using clonal analysis and molecular marker labeling, we identify a multipotent stem-cell pool at the foregut/midgut junction in the cardia (proventriculus). We found that daughter cells migrate upward either to anterior midgut or downward to esophagus and crop. The cardia functions as a gastric valve and the anterior midgut and crop together function as a stomach in Drosophila; therefore, we named the foregut/midgut stem cells as gastric stem cells (GaSC). We further found that JAK-STAT signaling regulates GaSCs' proliferation, Wingless signaling regulates GaSCs' self-renewal, and hedgehog signaling regulates GaSCs' differentiation. The differentiation pattern and genetic control of the Drosophila GaSCs suggest the possible similarity to mouse gastric stem cells. The identification of the multipotent stem cell pool in the gastric gland in Drosophila will facilitate studies of gastric stem cell regulation and transformation in mammal.