Sajeongjeon, Royal office hall at Gyeongbokgung Palace in Seoul, South Korea.

Sajeongjeon is the main hall of the pyeonjeon office complex at Gyeongbokgung Palace, standing behind Geunjeongjeon on a three-tiered stone platform. Its front is five bays wide and three deep, with a wider central bay, red-brown lattice doors and transom panels under a hipped grey-tiled roof with painted eaves brackets. Inside is one open room with a painted throne at the north center.

Sajeongjeon was completed in 1395, one of the first structures of Gyeongbokgung, and was first called Bopyeongcheong before receiving its present name from official Chŏng Tojŏn. It was enlarged in 1429, destroyed in the 1553 fire and rebuilt, then burned again in 1592 during the Imjin War. The present building was rebuilt in 1867 together with Geunjeongjeon and Gyeonghoeru; its interior was altered in 1915 when it served as an exhibition hall.

The name Sajeong, "Thinking of Good Deeds," was chosen by official Chŏng Tojŏn from a passage in the Chinese Book of Documents: since the world's principles are grasped when pondered and lost when not, the king was urged to think deeply before governing. The plaque was brushed by Cho Sŏg-u, Minister of Personnel, when the palace was rebuilt.

Access to this building requires a Gyeongbokgung Palace admission ticket, with entry through Gwanghwamun Gate. Guided tours available in multiple languages can help visitors understand the space and its historical function.

Unlike other palace buildings, this hall lacks traditional underfloor heating systems, suggesting it was used mainly during warmer seasons. This design choice reveals that the structure was specifically intended for seasonal administrative work.