The Black Watch, 3rd Battalion, Royal Regiment of Scotland (3 SCOTS) is an infantry battalion of the Royal Regiment of Scotland. The regiment was created as part of the Childers Reforms in 1881, when the 42nd (Royal Highland) Regiment of Foot (The Black Watch) was amalgamated with the 73rd (Perthshire) Regiment of Foot. It was known as The Black Watch (Royal Highlanders) from 1881 to 1931 and The Black Watch (Royal Highland Regiment) from 1931 to 2006. Part of the Scottish Division for administrative purposes from 1967, it was the senior Highland regiment. It has been part of the Scottish, Welsh and Irish Division for administrative purposes from 2017.

The source of the regiment's name is uncertain. In 1725, following the Jacobite rebellion of 1715, General George Wade was authorized by George I to form six "watch" companies to patrol the Highlands of Scotland, three from Clan Campbell, one from Clan Fraser of Lovat, one from Clan Munro and one from Clan Grant. These were to be "employed in disarming the Highlanders, preventing depredations, bringing criminals to justice, and hindering rebels and attainted persons from inhabiting that part of the kingdom." The force was known in Gaelic as Am Freiceadan Dubh, "the dark" or "black watch".

This epithet may have come from the uniform plaids of dark tartan with which the companies were provided. Other theories have been put forward; for instance, that the name referred to the "black hearts" of the pro-government militia who had sided with the "enemies of true Highland spirit",or that it came from their original duty in policing the Highlands, namely preventing "blackmail" (Highlanders demanding extortion payments to spare cattle herds).