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)

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 to form two battalions of the newly named Black Watch (Royal Highlanders). The 42nd became the 1st Battalion, and the 73rd became the 2nd Battalion.

In 1908, the Volunteers and Militia were reorganized nationally, with the former becoming the Territorial Force and the latter the Special Reserve; the regiment now had one Reserve and five Territorial battalions

7th Battalion in the Second World War

7th Battalion:
June 1942 - December 1942: North Africa
January 1943 - April 1943: North Africa. Record the same as 1st Battalion.
May 1943 - October 1943: Sicily. Record the same as 1st Battalion.
June 1944 - D-Day - May 1945. Record the same as 1st Battalion.After the capture of the 51st Highland Division at St Valéry in June 1940 no more than thirty members of the old 1st Battalion were available so they were reformed in the UK around a nucleus provided by the 9th Scottish Division., it was joined by the 5th and 7th Battalions which had not yet gone overseas.
June 1942: Sailed to Egypt
August 1942: Arrived via the Cape of Good Hope, the Red Sea and the Suez Canal.
23 October1942: The Battle of Alamein at 09:40hrs opened with a huge artillery barrage. All three Battalions advanced close behind through minefields, riffle and machine gun fire and barbed wire.
24 October 1942: By day break their first objectives had been reached but not without heavy casualties.
3 November 1942: The 1st Battalion attached to 154 Brigade with the 7th Battalion was withdrawn from the front. They became part of the force following the retreating Germans beyond Benghazi and Tobruk.
8 December 1942: The 7th Battalion along with the 1st Battalion were at the village of Mersa Brega. Objective was to circle around the village and cut the road off the other side. There were many casualties from the mines laid down by the Germans to cover their retreat but the operation was completed.
15 January 1943: Its next close contact with the enemy was at Buerat.
17 January 1943: They made a quick advance to Tripoli in order to secure another port to receive supplies, as supply line at Benghazi became under threat due to severe weather conditions.
February 1943: They had contact with the Germans near Medenine.
6 March 1943: The 1st Battalion came under attack and was very close to being overrun but the Germans decided to withdraw that night.
23 March 1943: The 1st Battalion was amongst units which took over from 50th Division on the south side of the Wadi, ready to attack.
26 March 1943: The Germans had withdrawn and the following day the Battalion along with other troops marched into the town, Gabes.
May 1943: The battalion was moved to Djidjelli in Algeria to be trained in amphibious landings.
10 July 1943: They landed just west of Pachino Point on the coast of Sicily.
8 September 1943: The Battalion crossed to the Italian mainland.
October 1943: They were shipped back to the UK.
After its return to the UK the battalion remained there in training for the invasion of France.
9 June 1944: The 1st Battalion sailed from Tilbury to Normandy.
19 June 1944: They came under heavy enemy shell and mortar fire in the (Wood) Bois de Bavent and suffered many casualties.
July 1944: The battalion was engaged at different times and ways in the great push north to help the Americans close the Falaise Gap.
2 Sept 1944: They were back in St Valéry.
14 Nov 1944: Operation Ascot Low Countries Holland
8 February 1945: It was one of the battalions leading the attack into Germany through the Reichswald. It was almost in continuous action over the next few weeks.
March (early) 1945: It was pulled out of the line to train for the crossing of the Rhine.
22 March 1945: The crossing of the Rhine was the last major engagement for the Battalion before VE-day.