This article needs additional citations for verification. (June 2019)
The list of ship commissionings in 1921 includes a chronological list of ships commissioned in 1921. In cases where no official commissioning ceremony was held, the date of service entry may be used instead.
|Date||Operator||Ship||Pennant||Class and type||Notes|
|May 9||Royal Navy||Tristram||Modified R-class destroyer||Scrapped|
|July 17||United States Navy||A-3||SS-4||Plunger-class submarine||at Cavite Navy Yard, Philippines, disposed of as a target ship and stricken in 1922 |
|July 25||United States Navy||A-5||SS-6||Plunger-class submarine||at Cavite Navy Yard, Philippines, disposed of as a target ship and stricken in 1922 |
|October 6||United States Navy||Aramis||SP-418||Patrol vessel||Tender and houseboat 1924-1933; Sold 1933|
|November 15||Royal Navy||Tirade||Modified R-class destroyer||Scrapped|
|December 1||French Navy||Foudre||Seaplane tender and training ship||date stricken; later scrapped|
|December 12||Royal Australian Navy||Australia||Indefatigable-class battlecruiser||Scuttled in 1924|
|unknown date||United States Navy||Ardent||SP-680||Patrol vessel/minesweeper||Sold|
- "A-3 (Submarine Torpedo Boat No. 4)". Dictionary of American Naval Fighting Ships. Naval History and Heritage Command. 31 August 2016. Retrieved 3 June 2019.
A-3 was assigned to the First Submarine Division, Torpedo Flotilla, Asiatic Fleet, and remained in active service with that unit until decommissioned at Cavite on 25 July 1921. During World War I, A-3 patrolled the waters off the entrance to Manila Bay. On 17 July 1920, she was given the identification number SS-4. Dismantled and used as a target by ships of the Asiatic Fleet, A-3 was stricken from the Naval Vessel Register on 16 January 1922.
- "A-5 (Submarine Torpedo Boat No. 6)". Dictionary of American Naval Fighting Ships. Naval History and Heritage Command. 31 August 2016. Retrieved 6 June 2019.
A-5, given the identification number SS-6 on 17 July 1920, was decommissioned on 25 July 1921. Earmarked as a target vessel, the submarine torpedo boat was stricken from the Naval Vessel Register on 16 January 1922.
|Ship events in 1921|