Viscount Thurso, of Ulbster in the County of Caithness, is a peerage title in the Peerage of the United Kingdom. It was created in 1952 for the Scottish Liberal politician Sir Archibald Sinclair, 4th Baronet, of Ulbster. The Baronetcy, of Ulbster in the County of Caithness, had been created in the Baronetage of Great Britain in 1786 for his great-great-grandfather, the Scottish politician and writer John Sinclair.

Sinclair Baronets of Ulbster (1786)

• Sir John Sinclair, 1st Baronet, of Ulbster (1754-1835)
• Sir George Sinclair, 2nd Baronet, of Ulbster (1790-1868)
• Sir John George Tollemache Sinclair, 3rd Baronet, of Ulbster (1824-1912)
• Sir Archibald Sinclair, 4th Baronet, of Ulbster (1890-1970) (created Viscount Thurso in 1952)

Viscounts Thurso (1952)

• Archibald Henry Macdonald Sinclair, 1st Viscount Thurso (1890-1970)
• Robin Macdonald Sinclair, 2nd Viscount Thurso (1922-1995)
• John Archibald Sinclair, 3rd Viscount Thurso (b. 1953) (known as 'John Thurso')

Heir apparent: the present holder's son Hon. James Alexander Robin Sinclair (b. January 14, 1984)

See also

• Veronica Linklater, Baroness Linklater of Butterstone