Queen Sinjeong (Korean: 신정왕후; Hanja: 神貞王后; 9 January 1809 – 23 May 1890), of the Pungyang Jo clan, was the only wife of Crown Prince Hyomyeong and mother of Heonjong of Joseon.

After the previous king died, she was known as Grand Queen Dowager Hyoyu (효유대왕대비), and served as nominal regent during Gojong's minority, between 1864 and 1873.

Although she left all de facto power to the King's father, Grand Internal Prince Heungseon, and only kept the formal title.

In 1819, she became Crown Princess Consort when she married Crown Prince Hyomyeong, thus granting her mother the royal title of “Internal Princess Consort Deokan” (덕안부부인; 德安府夫人) and her father, “Internal Prince Pungeun” (풍은부원군; 豊恩府院君).

The Crown Princess Consort gave birth to her only son, the future King Heonjeong, on 8 September 1827.

Through the influence of her mother-in-law, Queen Sunwon, her son married in 1837 to a daughter from her clan, the Andong Kim.

[1][page needed] Anti-Catholic in nature, the Pungyang Jo clan dominated the court when King Heonjeong blamed the Andong Kim clan for being soft on Catholics and launched a persecution, killing hundreds of Catholics, including three French missionary priests.

From those relatives, she selected Yi Won-beom, one of few living descendants of King Yeongjo and a second cousin once removed to Heonjong.

On July 28, 1849, Cheoljong ascended the throne in Changdeok Palace, and the Queen Dowager served as regent for two years.

As soon as news of Cheoljong's death reached Yi Ha-eung through his intricate network of spies in the palace, he and the Pungyang Jo clan took the hereditary royal seal — an object that was considered necessary for a legitimate reign to take place and aristocratic recognition to be received — effectively giving her absolute power to select the successor to the throne.

By the time Cheoljong's death had become a known fact, the Andong Kim clan was powerless according to law as the seal lay in the hands of the Grand Queen Dowager Sinjeong.

On 21 January, Yi Myeong-bok was enthroned as King Gojong, and Dowager Queen Sinjeong began her regency.

[5][page needed] Since Gojong was so young, Queen Sinjeong invited the Daewongun to assist his son in ruling.