RMS Atrato was a UK iron-hulled steamship. She was built in 1853 for the Royal Mail Steam Packet Company as a side-wheel paddle steamer, and at the time of her launch was the world's largest passenger ship. In 1870 RMSP traded Atrato in, causing her to lose the status of "Royal Mail Ship". She was converted to a single screw ship with a compound steam engine in 1872, and placed on the Aberdeen Line that chartered her to run to Victoria and New Zealand. In 1880 she was renamed Rochester before sinking four years later in 1884 by running aground.

The Royal Mail Steam Packet Company was a British shipping company founded in London in 1839 by a Scot, James MacQueen. The line's motto was Per Mare Ubique. After a troubled start, it became the largest shipping group in the world in 1927 when it took over the White Star Line. The company was liquidated and its assets taken over by the newly formed Royal Mail Lines in 1932 after financial trouble and scandal; over the years RML declined to no more than the name of a service run by former rival Hamburg Süd.