SS Great Britain is a museum ship and former passenger steamship, which was advanced for her time.

She was the longest passenger ship in the world from 1845 to 1854.

She was designed by Isambard Kingdom Brunel (1806–1859), for the Great Western Steamship Company's transatlantic service between Bristol and New York City.

While other ships had been built of iron or equipped with a screw propeller, Great Britain was the first to combine these features in a large ocean-going ship.

She was the first iron steamer to cross the Atlantic Ocean, which she did in 1845, in the time of 14 days.

The ship is 322 ft (98 m) in length and has a 3,400-ton displacement.

She was powered by two inclined 2 cylinder engines of the direct-acting type, with twin high pressure cylinders (diameter uncertain) and twin low pressure cylinders 88 in (220 cm) bore, all of 6-foot (1.8 m) stroke cylinders.

She was also provided with secondary masts for sail power. The four decks provided accommodation for a crew of 120, plus 360 passengers who were provided with cabins, and dining and promenade saloons.

When launched in 1843, Great Britain was by far the largest vessel afloat.

But her protracted construction time of six years (1839–1845) and high cost had left her owners in a difficult financial position, and they were forced out of business in 1846, having spent all their remaining funds refloating the ship after she ran aground at Dundrum Bay in County Down near Newcastle in what is now Northern Ireland, after a navigation error.

In 1852 she was sold for salvage and repaired. 

Great Britain later carried thousands of immigrants to Australia from 1852 until being converted to all-sail in 1881. Three years later, she was retired to the Falkland Islands, where she was used as a warehouse, quarantine ship and coal hulk until she was scuttled and sunk in 1937, 98 years since being laid down.

In 1970, after Great Britain had been under water and abandoned for 33 years, Sir Jack Arnold Hayward, OBE (1923–2015) paid for the vessel to be raised and repaired enough to be towed north through the Atlantic back to the United Kingdom, and returned to the Bristol dry dock where she had been built 127 years earlier.

Hayward was a prominent businessman, developer, philanthropist and owner of the English football club Wolverhampton Wanderers.

Now listed as part of the National Historic Fleet, Great Britain is a visitor attraction and museum ship in Bristol Harbour, with between 150,000 and 200,000 visitors annually.