Which ship was the first purpose-built steamship to provide regular transatlantic service?

SS Great Western was the first purpose-built steamship to provide regular transatlantic service.

Built for the Great Western Steamship Company, the 1838 ship was designed by the British engineer Isambard Kingdom Brunel. She was constructed at Bristol and used both steam power and sails, a combination common during the early transition from sailing ships to steamships.

Great Western began service between Bristol and New York in April 1838. Her first voyage demonstrated that a large steamship could operate reliably across the Atlantic, helping establish regular steam-powered passenger travel. She was later joined by SS Great Britain, another Brunel-designed vessel.

SS Savannah had crossed the Atlantic partly under steam in 1819, but it was not a regular transatlantic liner. That distinction belongs to Great Western, which was purpose-built for scheduled service rather than merely experimenting with steam propulsion.