Thenae or Thenai (Ancient Greek: Θεναί), also written Thaena and Thaenae, was a Carthaginian and Roman town (civitas) located in or near Thyna, now a suburb of Sfax on the Mediterranean coast of southeastern Tunisia.

Along with the rest of ancient Tunisia, it passed into Carthaginian and then Roman control during the time of the Punic Wars.

Thenae issued its own bronze coins around the time of Julius Caesar and Augustus, with a female head (either Serapis or Astarte) obverse and a four-columned temple reverse.

According to a life of St Fulgentius, a council was held at Thenae (Latin: Thenitanum Concilium).

There are six documented bishops of the ancient diocese: Today, Thenae survives as a titular see of the Roman Catholic Church.