Shetlopedia - The Shetland Encyclopaedia
- Publication of, Shetland and the Shetlanders, or the Northern Circuit, by Catherine Sinclair.
- c.1840 Tar-barrelling introduced as part of the Antonsmas celebrations
- The first bank in Shetland, the Union Bank, was established, located at 6 Clairmont Place, the building that now houses the Alder Lodge Guest House.
- The Topographical, Statistical and Historical Gazeteer of Scotland reported the following figures for Shetland fishery for the year ending April 5th, 1840: Lerwick 740 boats, 3,528 men & boys employed. Unst 139 boats and 651 men & boys, Walls 306 boats, 1,766 employed. Lerwick produced 16,000 barrels of herring, Unst 5,319 and Walls 4,366.
- John Cheyne (1) of Tangwick, the fourth Laird Cheyne of Tangwick, died.
The Borussia, known locally as "the rye ship", a sail brig laden with a cargo of mats and rye, of Stralsund, Prussia (now Germany), from Archangel, Russia for Rotterdam, The Netherlands wrecked at Cross Geo, Harold's Wick, Unst. The Captain and at least some of the crew perished, but some of the crew were also saved, there are conflicting accounts of the exact numbers. The ship's gear and much of the cargo was salvaged, but the wreck was condemned.
Henry Cheyne of Tangwick, the fifth Laird Cheyne of Tangwick, married Barbara, eldest daughter of William Hay, of Laxfirth.
- 17th or 21st
The wooden hulled sailing ship Brian O'Lin, (or Brian O'Linn), wrecked and sunk near Scalloway.
An unidentified vessel, laden with a cargo of timber, reported aground bottom up on the Hoevdi Grund, Foula. Crew persumed to have perished.