Union was an American sloop built in Somerset, Massachusetts in 1792. It is best known for its circumnavigation of the world, 1794–1796, under the maritime fur trader John Boit.

The sloop Union was 94 tons burthen, 65 ft 5 in (19.9 m) length overall, 19 ft 9 in (6.0 m) beam, and 8 ft 5 in (2.6 m) depth. She had a crew of 22, one deck, one mast, and a fore-and-aft rig. Her armament was 10 carriage guns, which were a mix of 6-pounders and 3-pounders, and 8 swivel guns mounted on the rails.

Union was built in 1792 and registered on 8 July 1793. Her original owners were William Burroughs (merchant), John Nicolas (trader), Benjamin Hicks (mariner), and John Finch. She was re-registered on 26 August 1794 under the new owners Caleb Garner (merchant of Newport, Rhode Island), Crowell Hatch and Peter Brooks (merchants of Boston), and master John Boit. After Boit's voyage Union was sold on 22 July 1796, in Boston.

John Boit had served as fifth mate on the second voyage of the Columbia Rediviva under Captain Robert Gray, 1790–1793. Shortly after returning to Boston Boit was given command of the Union for another maritime fur trading voyage to the Pacific Northwest and China. The sloop was owned by three investors including Boit's brother-in-law Crowell Hatch, who had also been an investor in the two voyages of Columbia Redivia, under Robert Gray and John Kendrick.

Boit sailed Union from Newport, Rhode Island, on 1 August 1794. He passed the Cape Verde Islands without stopping in October. The Falkland Islands were reached near the end of the year. Boit remained in the Falklands for about three weeks before leaving on 23 January 1795. Rounding Cape Horn the Union reached its southernmost latitude on 4 February 1795.

On 16 May 1795 he arrived at Columbia Cove, near Nasparti Inlet in Checleset Bay, on the west coast of Vancouver Island near Brooks Peninsula. He had been there three years before with Captain Gray on Columbia. After acquiring all the sea otter he could, he sailed south to Nootka Sound. From there he sailed north to Haida Gwaii to trade with the native Haida for sea otter furs. After trading with the Haida in the vicinity of Houston Stewart Channel and the village of Ninstints the Union cruised north up the eastern side of Haida Gwaii to the vicinity of the village known as Cumshewa. Then he returned south to Ninstints and cruised up the western side of Haida Gwaii until reaching the northern end in June, 1795. Boit traded with the Haida of Chief Cuneah in the area near Cloak Bay, Langara Island, and villages such as Dadens and Kiusta. Then Boit sailed the Union south to the Strait of Juan de Fuca, the Columbia River, and Tillamook Bay, again trading for sea otter furs. For nine days he attempted to enter the Columbia River. But the weather was against him and he nearly lost the Union on the dangerous Columbia Bar before giving up in disappointment.

From Tillamook Bay Boit sailed north again, stopping briefly at Nootka Sound. By August, 1795, Union was again cruising the southeast coast of Haida Gwaii and the west coast of Vancouver Island.

On 12 September 1795 Boit, having finished his fur trading, sailed from Columbia Cove, making for the Hawaiian Islands and Guangzhou (Canton), China.