Tabas (Persian: طبس) is a city in the Central District of Tabas County, South Khorasan province, Iran, serving as capital of both the county and the district.

The history of Tabas dates back to pre-Islamic times. It was an important outpost of the Sassanid empire.

Due to its strategic location at the edge of the Great Salt Desert, and at the confluence of many roads, the geographer al-Baladhuri called the city "the Gate of Khurasan". In the early Islamic period it was known as Tabas al-Tamr (lit. 'Tabas of the Dates') due to a large forest of date palms that grew there, and later as Tabas Gilaki after a famous governor of the city, Abu'l-Hasan ibn Muhammad Gilaki, who in the mid-11th century had pacified the region. Along with the town of Tabas-e Masina further east, it gave its name to the local district, Tabasayn. In the 10th–11th centuries, the town is described as well fortified, with several villages around. Medieval and geographers note that it was amply supplied with water due to underground wells; the town even featured hot baths, and extensive lemon and orange plantations. In the late 11th century, it became part of the Nizari Ismaili state, and was besieged by the Seljuk Turks under Ahmad Sanjar in 1102 during the Nizari-Seljuk conflicts.

Tabas was spared when the Mongols attacked Iran. It had a local government incorporating not only Tabas but also Tun (Ferdows) and Gonabad. After the death of Nader Shah in 1747, it as under the control of the Zangu'i Arabs as an independent state which included nearby Tun. For a time they even kidnapped Nader Mirza Afshar and placed the Kurds of Khabushan in control of Mashhad.

In 1978, the 7.4 M_w  Tabas earthquake affected the city with a maximum Mercalli intensity of IX (Violent). At least 15,000 people were killed. Since then, the city has been rebuilt with many new streets, parks and public buildings.

The failed rescue American operation Operation Eagle Claw on 24–25 April 1980 to free American hostages in Tehran occurred near Tabas in Tabas Country about 127km southwest of Tabas town by the road to Yazd location (33.07020674739667;55.89196171977231). In Iran, the operation is called amaliat tabas (Tabas operation), and the significance and aftermath of the failed operation made the city Tabas known in almost every corner of Iran. The Tabas air defense system is accordingly named so.

At first, Tabas County was part of Khorasan province. It became a part of Yazd province in 2001, joining South Khorasan province in 2013.

The people of Tabas speak a Khorasani accent of Persian that sounds somewhat different from the standard Iranian version ("Tehrani accent").^{[citation needed]}