Saleh or Salih (Arabic: صَالِحٌ‎, romanized: Ṣāliḥ) is a prophet mentioned in the Qur'an who prophesied to the tribe of Thamud in ancient Arabia, before the lifetime of the Islamic prophet Muhammad. The story of Salih is linked to the story of the She-Camel of God, which was the gift given by God to the people of Thamud when they desired a miracle to confirm that Salih was truly a prophet.

The Thamud were a tribal confederation in the northwestern region of the Arabian Peninsula, mentioned in Assyrian sources in the time of Sargon II. The tribe's name continues to appear in documents into the fourth century CE, but by the sixth century they were regarded as a group that had vanished long ago.

According to the Quran, the city that Saleh was sent to was called Al-Ḥijr (Arabic: ٱلْحِجْرْ, lit. 'The Stonetown'), which corresponds to the Nabataean city of Hegra. The city rose to prominence around the 1st century AD as an important site in the regional caravan trade. Adjacent to the city were large, decorated rock-cut tombs used by members of various religious groups. At an unknown point in ancient times, the site was abandoned and possibly functionally replaced by Al-'Ula. The site has been referred to as Mada'in Salih (Arabic: ﻣﺪﺍﺋﻦ ﺻﺎﻟﺢ, romanized: madāʼin Ṣāliḥ, lit. 'the cities of Saleh') since the era of Muhammad and was named after his predecessor Salih.

Saleh is not mentioned in any historical texts or in any of the Abrahamic scriptures that precede the Qur'an, but the account of Thamud's destruction may have been well known in ancient Arabia. The tribe's name is used in ancient Arabian poetry as a metaphor for "the transience of all things".

According to Muslim tradition, the people of Thamud virtually relied upon Saleh for support. He was chosen by God as a prophet (Arabic: نبي, romanized: nabi) and sent to preach against the selfishness of the wealthy and to condemn the practice of shirk (Arabic: شِرْك, lit. 'polytheism'). Although Saleh preached for a sustained period of time, the people of Thamud refused to hear his warning and instead began to ask Saleh to perform a miracle for them. They said: “O Ṣâliḥ! We truly had high hopes in you before this. How dare you forbid us to worship what our forefathers had worshipped? We are certainly in alarming doubt about what you are inviting us to.”

Saleh reminded his people of the castles and palaces they built out of stone, and of their technological superiority over neighbouring communities. Furthermore, he told them about their ancestors, the ʿĀd tribe, and how they too were destroyed for their sins. Some of the people of Thamud believed Saleh's words, but the tribal leaders refused to listen to him and continued to demand that he demonstrate a miracle to prove his prophethood.

In response, God gave the Thamud a blessed she-camel (Arabic: نَاقة, romanized: naaqah, lit. 'female camel'), as both a means of sustenance and a test. The tribe was told to allow the camel to graze peacefully and avoid harming her. But in defiance of Saleh's warning, the people of the tribe hamstrung the camel. Saleh informed them that they had only three more days to live before the wrath of God descended upon them. The people of the city were remorseful, but their crime could not be undone, and all the disbelieving people in the city were killed in an earthquake. Al-Hijr was rendered uninhabited and remained in ruins for all time thereafter. Saleh himself and the few believers who followed him survived.

The story is expanded upon in Sūrat an-Naml of the Qur'an. Whilst the she-camel is not mentioned explicitly in this chapter, it states that nine men plotted to kill Salih and his whole family, a crime for which they were struck down by God three days later.