Tlos (Lycian: 𐊗𐊍𐊀𐊇𐊀 Tlawa, Hittite: 𒁕𒆷𒉿 Dalawa, Ancient Greek: Τλώς or Τλῶς) was an ancient Lycian city near the modern town of Seydikemer in the Mugla Province of southern Turkey, some 4 kilometres northwest of Saklıkent Gorge.

Tlos lies on the east side of the Xanthos valley atop a rocky outcrop that slopes up from a plateau from a modern village and ends on the west, north and northeast in almost perpendicular cliffs.

[3] It is known as 'Tlawa' in local Lycian inscriptions and as ‘Dalawa’ in the Hittite sources which shows the importance of the city as early as the 15th century BC in the Late Bronze Age.

Later, in the Hellenistic period, its importance is shown by being one of the six principal cities of the Lycian League to which in 168 BC Rome granted autonomy instead of dependence on Rhodes.

Inscriptions reveal that citizens of Tlos were divided into demes (social subdivisions), and the names of three of them are known: Bellerophon, Iobates and Sarpedon, famous Lycian heroes of legend.

[6] Tlos was rediscovered by Charles Fellows in 1838 and was followed by the explorer Thomas Abel Brimage Spratt, who thought that "a grander site for a great city could scarcely have been selected in all Lycia."

[7] The influence of many cultures upon Tlos has resulted in a patchwork of buildings dominated by an acropolis and fortress.

In early Lycian times the city's settlement was likely concentrated on the southern and western slopes.

Wide terraces with cisterns and the back walls of buildings carved from the rock are found there, as well as an agora, a theatre for plays and concerts, public Roman baths and the remains of an early Byzantine church.

The top of the hill was chosen for the ruler's palace complex dating from the early Classical period.

The sanctuary thought to be for the local Lycian deity Trggas stands on a platform formed by quarrying the rock on the northern slope of the acropolis next to the palace.

Architectural details and an inscription mentioning its restoration in the 1st century BC indicate that it might have been built in the Hellenistic period.

It was once one of the major theatres of Lycia in terms of its architectural design, with its three-storey stage and large auditorium (cavea).

The diameter of the orchestra, slightly exceeding a semicircular shape, is 20.5 m. The stone seats reserved for VIPs (proedria) are placed above the horizontal walkway.

Tlos became a Christian bishopric, a suffragan of the metropolitan see of Mira, capital of the Roman province of Lycia.