SS Royal William was a Canadian side-wheel paddle steamship that is sometimes credited with the first crossing of the Atlantic Ocean almost entirely under steam power, in 1833. She was the largest passenger ship in the world from 1831 to 1839, where it was then passed by the SS Great Western. Earlier vessels that crossed partially under steam include the British-built Dutch-owned Curaçao in 1827 and the sail-steam hybrid SS Savannah in 1819.