Cilly, Or Cilli (Anc. Celela; Slovenish, Ceje), a town of Austria, in the crown land of Styria, capital of an extensive circle, situated near the junction of the Kodenbach with the San, 36 m. E. N E. of Laibach; pop. in 1870, 4,203. It is an old town, surrounded by walls and towers, and contains a quaint parish church, having a fine altar and a side chapel with a Gothic throne and ciborium of carved stone. There are ruins of an ancient castle, long the residence of the counts of Cilly, and of the Lazarist convent of St. Joseph, with two towers. Eemains of Roman architecture have also been found here. The castle, Neu Cilly, is 4 m. outside of the town. The principal trade is in wine, cereals, cattle, and coal. There are in the vicinity extensive coal fields and deposits of spathic and haematite iron ore; an English company was established in 1807 for manufacturing steel and iron. - The site of Cilly has been identified with that of Celeia or Caleia, a city at the S. E. extremity of Noricum, and with the Roman colony of Caleia Claudia, which grew out of the ruins of the more ancient city.
During the middle ages it was the capital of the Slavonian district of Zellia. It was ruled by Austrian dukes from 1146 to 1331, and in 1339 it became the capital of the newly created county of Cilly. The assassination of Count Ulric at Belgrade in 1450 putting an end to that line, it has since been Austrian.