Black Watch – also known as the Universal or Government tartan. Whilst being worn by the 42nd Black Watch Regiment (The Royal Highland Regiment), since 1739 this tartan has formed the basis upon which many other Regiment's tartans were designed, most notably Gordon (Gordon Highlanders), MacKenzie (Seaforth Highlanders and the Highland Light Infantry), Sutherland (Princess Louise's Argyll and Sutherland Highlanders).
The belief that the Black Watch tartan was based on the Campbell Tartan is disputed by several experts. (The Black Watch Pipers wear the Stewart Royal Tartan).
The "Watches" were a system of policing to prevent cattle lifting and the Black Watch tartan was eminently suitable in this role.

Also worn by
The Royal Scots (The Royal Regiment) until 1901 when they adopted the Hunting Stewart.
The Gordon Highlanders (75th & 92nd  Foot), wore the Black Watch tartan prior to 1778 after which a yellow line was added.
The 91st Argyllshire Highlanders, raised in 1794.
The Argyll & Sutherland Highlanders (the tartan was referred to as the Sutherland tartan but was the Black Watch in a slightly lighter shade)
Breadalbane Fencibles 1793 wore the Black Watch at first but later added two yellow lines .It became called the Campbell of Breadalbane
New South Wales Scottish (Australia)
Royal New South Wales Regiment (Australia)
Dunedin Highland Rifle Volunteers (New Zealand)
Wellington Highlanders (New Zealand)
Auckland Highland Rifle Volunteers (New Zealand)
1st Armoured Car Regiment (New Zealand Scottish)
Royal Durban Light Infantry (South Africa)
Black Watch (The Royal Highland Regiment) of Canada