Haixiu 121 class tug is a class of naval auxiliary ship currently in service with the People's Liberation Army Navy (PLAN).

[1] The designation Haixiu 121 is unique in that it is different from the usual Chinese naming convention for ships in military service.

Ordinarily, auxiliary ships in PLAN service are designated by a combination of two or more Chinese characters followed by three-digit number.

The second indicates the function the ship performs, usually 拖; tuō for tugboats.

Haixiu 121 is a tug, but is designated a repair ship 海修; hǎi xiū).