The China Railways QJ (Chinese: 前进; pinyin: Qián Jìn; lit. 'To go forward" or "to advance') is a class of 2-10-2 type steam locomotives used primarily for heavy freight trains. They were introduced in 1956 by the Dalian Locomotive Works, and all of the production locomotives were built by the Datong Locomotive Works. The prototypes and early production of the class were designated HP (Chinese: 和平; pinyin: Hé Píng; lit. 'peace'), being redesignated as FD (Chinese: 反帝; pinyin: Fǎn Dì; lit. 'Anti-Imperialism') class during the Cultural Revolution, before becoming the QJ class in 1971.

The class became the primary mainline freight locomotive on the Chinese rail network by the 1980s. Manufactured until 1988, a total of 4,717 were produced. After the end of steam on the national Chinese railway network, many QJ locomotives were used on industrial lines, as well as on the Jitong railway, and the latter also phased out their QJs in 2005. Several members of the class have been preserved in several countries.

As early as 1954, the Dalian Locomotive Works began studying 2-10-2 locomotive designs to assist China Railways' increasing freight traffic. At the time, the People's Republic of China was allied with the Soviet Union, and as part of the latter's economic aid for the former, Dalian's engineering process was assisted by Soviet experts with Soviet technology. Dalian's new 2-10-2 design was consequently based upon the Soviet class OR21, a more powerful variant of the class OR18.

The first prototype 2-10-2, HP-0001, was completed by Dalian on 18 September 1956, and it was designated an HP (Chinese: 和平; pinyin: Hé Píng; lit. 'peace'). In accordance with the design, the HP prototype was identical to the OR21s, as it came with all-boxpok driving wheels (diameter of 1,500 millimetres (59 in), flangeless center driving wheels, an all-welded boiler (diameter of 2,010 millimetres (79 in), and an operating boiler pressure of 1,471 kilopascals (213.4 psi), and it could generate a tractive force of 33,290 kilograms-force (73,400 lbf). One difference from the OR designs was that the HP also included a delta trailing truck akin to those on another Soviet 2-10-2 series, the class FD.

From 1956 to 1961, 41 additional prototype HPs were also built for testing: four more (HP-0002–HP-0005) by Dalian; eight (HP-1001–HP-1008) by the Tangshan Locomotive and Rolling Stock Works; six (HP-1501–HP-1506) by the Shenyang Locomotive Factory; three (HP-2001–HP-2003) by the Mudanjiang Locomotive Factory; two (HP-3001–HP-3002) by the Changchun Locomotive Factory; and eighteen (HP-3501–HP-3518) by the Datong Locomotive Works. The latter prototypes were the very first steam locomotives to be built by Datong.

While the prototypes were being developed and tested, China Railways acquired 1,000 secondhand class FDs from the Soviet Railways in 1958—with another 50 in 1961—as stopgap measures for their increasing freight traffic, until production on the HPs were able to begin.

After the final prototypes were completed, multiple modifications were made to the HP's boiler design. The boiler barrel diameter was enlarged to 2,100 millimetres (83 in); the smokebox and blast pipe orifice were enlarged to improve drafting; a combustion chamber, which the prototypes lacked, was installed in the firebox to improve combustion; the number of tubes was increased, while the tube length was decreased from the firebox tube plate being extended past the grate; and the maximum cutoff was increased to 72%.

The first locomotive with the design modifications, HP-101, was completed by Datong on 28 September 1964. After further test runs, Datong officially began production on the rest of the HPs, beginning with HP-102 in April 1965. In September 1966, amidst the Cultural Revolution, the HPs were re-designated as the FD class (反帝 Fandi meaning 'anti-imperialism'), and then in 1971, the class was re-designated again as the QJ class (Qian Jin, meaning 'march forward' or 'progress').