A gabbai (Hebrew: גבאי), sometimes spelled gabay, is also known as shamash (שמש, sometimes spelled shamas) or warden (UK, similar to churchwarden) is a beadle or sexton, a person who assists in the running of synagogue services in some way. The role may be undertaken on a voluntary or paid basis. A shamash (literally 'servant') or gabbai can also mean an assistant to a rabbi (particularly the secretary or personal assistant to a Hasidic rebbe).
In ma'amad, the Council of Elders (or "the board of directors") of the communities of Sephardi Jews, the position of gabbai was that of the treasurer.