Thennesus was a town in the Roman province of Augustamnica Prima.
[1] It is today called Tell-Tenis, Tell-Tannis or Qôm-Tannis, at the extremity of an island in Lake Menzaleh, near the Suez Canal.
Its bishopric was a suffragan see of Pelusium, the capital and metropolitan see of the province.
Its inhabitants were given solely to commerce, lacking arable land.
In 451 Heron, another of its bishops, was condemned by the Council of Chalcedon for not having anathematized the Patriarch Dioscorus.