The Britannia class was the Cunard Line's initial fleet of wooden paddlers that established the first year round scheduled Atlantic steamship service in 1840.

Britannia, Acadia and Caledonia entered service in 1840 and Columbia in 1841 enabling Cunard to provide the dependable schedule of sailings required under his mail contracts with the Admiralty.

[1] Cunard's ships were reduced versions of Great Western and only carried 115 passengers in conditions that Charles Dickens unfavourably likened to a "gigantic hearse".

[2] In 1849 and 1850, the surviving original units along with Hibernia were sold to foreign navies after completing forty round trips for Cunard.

[2] In his initial negotiations with Admiral Parry, Samuel Cunard contemplated a fortnightly service from Liverpool to Halifax and onto Boston using three 800 GRT steamers.

Unlike most other Atlantic steamers, Britannia's boilers were located aft of her engines and paddle wheels, resulting in a unique profile.

A special padded deck house had the ship's cow and overturned boats protected vegetables from the weather.

"[2]Describing the cabin, Dickens wrote: "..deducting the two berths, one above the other (the top one a most inaccessible shelf) than which nothing smaller for sleeping in was ever made except coffins, it was no bigger than one of those hackney cabriolets which have the door behind and soot their fares out, like sacks of coals, upon the pavement.

Cunard quickly realized that five units were required to maintain the fortnightly service and in 1843 he commissioned an enhanced Britannia with an additional 300 hp (220 kW).

When that navy was dissolved, Ersherzog Johann was sold to W. A. Fritze and Company of Bremen, Germany's first oceangoing steamship venture.

On 2 July 1843, she was wrecked on Devil's Limb Reef at Seal Island, Nova Scotia, without loss of life.

She held the Blue Riband for the fastest westbound Atlantic voyage from July 1845 until America won the record in June 1848.

After serving as a trooper in the Crimean War, Cambria was briefly placed back on the Boston service until Persia was commissioned.