Celtic was launched on 4 April 1901 from the Harland and Wolff shipyards in Belfast, and set off on her maiden voyage from Liverpool to New York City on 26 July.


She and her three sisters proved to be immensely popular with
travelers, particularly immigrants. During the infamous 1904 Rate War
she set the record for the highest number of passengers carried in a
single crossing in White Star's history. She arrived in New York on 16
September fully booked with 2,957 passengers on board.


At the beginning of the First World War, Celtic was converted into an armed merchant cruiser; however since the vessel had a high fuel consumption it was decided to convert her into a troop ship in January 1916 when she was used to carry soldiers to Egypt. She was put back on the transatlantic route in March 1916.

In 1917, Celtic struck a mine off the Isle of Man. Seventeen people on board were killed, but Celtic survived. A number of passengers were rescued by the London and North Western Railway ship Slieve Bawn. Celtic was towed to Peel Bay and repaired in Belfast. In March 1918, U-Boat UB-77 torpedoed Celtic in the Irish Sea. Six people on board were killed, but again Celtic remained afloat. Eventually the damaged vessel was towed to Liverpool and repaired again.

After the war, Celtic was involved in two collisions. The first incident occurred in 1925 while in the Mersey, when she accidentally rammed the Coast Line’s ship Hampshire Coast. Both vessels suffered only minor damage. The second collision took place on 29 January 1927, when Celtic was rammed in thick fog by the American Diamond Lines' Anaconda off Fire Island.

Early on 10 December 1928,^[​6] Celtic became stranded on the Cow and Calf rocks, adjacent to Roches Point as she approached Cobh with more than 200 passengers aboard. The Ballycotton Lifeboat T.P.Hearne 2, along with tugs, a destroyer and local life-saving teams, arrived. Tenders from Cobh disembarked the passengers.^[​7] Seven thousand tons of cargo were scattered. A salvage team from Cox and Danks
was provided to attempt recovery, but several men died after a hold
loaded with grain and flooded with seawater was found to have filled
with toxic fumes; due to structural failures it was judged the ship
could not be moved or salvaged, and was abandoned to the insurance
company who declared the ship to be a total loss. Celtic was completely dismantled for scrap by 1933.