The "Big Four" were a quartet of early-20th-century 20,000-ton ocean liners built by the Harland & Wolff shipyard for the White Star Line, to be the largest and most luxurious ships afloat.

In 1899, White Star Line commissioned the RMS Oceanic, which exceeded the SS Great Eastern in length but not tonnage.

Instead, resources were transferred to the company's new project; to build the grandest fleet of ships that had ever sailed the seas, the "Big Four".

[2][incomplete short citation] The first of the four vessels was named Celtic, and was ordered by Thomas Ismay before his death.

[3][incomplete short citation] The popularity of White Star's "Big Four" was eventually overtaken by Cunard's Lusitania and Mauretania, both of which were larger than the Adriatic, at 24,541 gross register tons the largest and also the fastest of the "Big Four", but which was superseded in size before her launch by Lusitania.

Lastly the Red Star Line's SS Lapland, at a more economical 17,000 tons, was a virtual sister ship to the "Big Four" in her layout and dimensions.

After the sinking it was reported that J. Bruce Ismay, managing director of the White Star line, had attempted to arrange, by wireless with the White Star New York offices, to delay the sailing of Cedric until Carpathia arrived in port so that he and the surviving crew members of Titanic could return to England without setting foot in the United States.

On 30 September 1923, Cedric collided with RMS Scythia of the Cunard Line in Queenstown harbour during dense fog.

[11] Baltic was commonly accompanied by White Star tender SS Magnetic, which serviced her throughout most of her career.

She was the largest, the fastest, and the most luxurious of the Big Four, being the first ocean liner to have an indoor swimming pool and a Victorian-style Turkish bath.

[13] Adriatic was devoted full-time to cruising from 1933, and was retired the following year, then sold by the White Star Line for scrapping in Japan in 1935.