Shen Kuo (Chinese: 沈括; 1031–1095) or Shen Gua, courtesy name Cunzhong (存中) and pseudonym Mengqi (now usually given as Mengxi) Weng (夢溪翁), was a Chinese polymath, scientist, and statesman of the Northern Song dynasty. Shen was a master in many fields of study including mathematics, optics, and horology. In his career as a civil servant, he became a finance minister, governmental state inspector, head official for the Bureau of Astronomy in the Song court, Assistant Minister of Imperial Hospitality, and also served as an academic chancellor. At court his political allegiance was to the Reformist faction known as the New Policies Group, headed by Chancellor Wang Anshi (1021–1085).

In his Dream Pool Essays or Dream Torrent Essays (夢溪筆談; Mengxi Bitan) of 1088, Shen was the first to describe the magnetic needle compass, which would be used for navigation (first described in Europe by Alexander Neckam in 1187). Shen discovered the concept of true north in terms of magnetic declination towards the north pole, with experimentation of suspended magnetic needles and "the improved meridian determined by Shen's [astronomical] measurement of the distance between the pole star and true north". This was the decisive step in human history to make compasses more useful for navigation, and may have been a concept unknown in Europe for another four hundred years (evidence of German sundials made circa 1450 show markings similar to Chinese geomancers' compasses in regard to declination).

Alongside his colleague Wei Pu, Shen planned to map the orbital paths of the Moon and the planets in an intensive five-year project involving daily observations, yet this was thwarted by political opponents at court. To aid his work in astronomy, Shen Kuo made improved designs of the armillary sphere, gnomon, sighting tube, and invented a new type of inflow water clock. Shen Kuo devised a geological hypothesis for land formation (geomorphology), based upon findings of inland marine fossils, knowledge of soil erosion, and the deposition of silt. He also proposed a hypothesis of gradual climate change, after observing ancient petrified bamboos that were preserved underground in a dry northern habitat that would not support bamboo growth in his time. He was the first literary figure in China to mention the use of the drydock to repair boats suspended out of water, and also wrote of the effectiveness of the relatively new invention of the canal pound lock. Although not the first to invent camera obscura, Shen noted the relation of the focal point of a concave mirror and that of the pinhole. Shen wrote extensively about movable type printing invented by Bi Sheng (990–1051), and because of his written works the legacy of Bi Sheng and the modern understanding of the earliest movable type has been handed down to later generations. Following an old tradition in China, Shen created a raised-relief map while inspecting borderlands. His description of an ancient crossbow mechanism he unearthed as an amateur archaeologist proved to be a Jacob's staff, a surveying tool which was not known in Europe until described by Levi ben Gerson in 1321.

Shen Kuo wrote several other books besides the Dream Pool Essays, yet much of the writing in his other books has not survived. Some of Shen's poetry was preserved in posthumous written works. Although much of his focus was on technical and scientific issues, he had an interest in divination and the supernatural, the latter including his vivid description of unidentified flying objects from eyewitness testimony. He also wrote commentary on ancient Daoist and Confucian texts.

Shen Kuo was born in Qiantang (modern-day Hangzhou) in the year 1031. His father Shen Zhou (沈周; 978–1052) was a somewhat lower-class gentry figure serving in official posts on the provincial level; his mother was from a family of equal status in Suzhou, with her maiden name being Xu (許). Shen Kuo received his initial childhood education from his mother, which was a common practice in China during this period. She was very educated herself, teaching Kuo and his brother Pi (披) the military doctrines of her own elder brother Xu Dong (許洞; 975–1016). Since Shen was unable to boast of a prominent familial clan history like many of his elite peers born in the north, he was forced to rely on his wit and stern determination to achieve in his studies, subsequently passing the imperial examinations and enter the challenging and sophisticated life of an exam-drafted state bureaucrat.

From about 1040 AD, Shen's family moved around Sichuan province and finally to the international seaport at Xiamen, where Shen's father accepted minor provincial posts in each new location. Shen Zhou also served several years in the prestigious capital judiciary, the equivalent of a national supreme court. Shen Kuo took notice of the various towns and rural features of China as his family traveled, while he became interested during his youth in the diverse topography of the land. He also observed the intriguing aspects of his father's engagement in administrative governance and the managerial problems involved; these experiences had a deep impact on him as he later became a government official. Since he often became ill as a child, Shen Kuo also developed a natural curiosity about medicine and pharmaceutics.

Shen Zhou died in the late winter of 1051 (or early 1052), when his son Shen Kuo was 21 years old. Shen Kuo grieved for his father, and following Confucian ethics, remained inactive in a state of mourning for three years until 1054 (or early 1055). As of 1054, Shen began serving in minor local governmental posts. However, his natural abilities to plan, organize, and design were proven early in life; one example is his design and supervision of the hydraulic drainage of an embankment system, which converted some one hundred thousand acres (400 km²) of swampland into prime farmland. Shen Kuo noted that the success of the silt fertilization method relied upon the effective operation of sluice gates of irrigation canals.

In 1063 Shen Kuo successfully passed the imperial examinations, the difficult national-level standard test that every high official was required to pass in order to enter the governmental system. He not only passed the exam however, but was placed into the higher category of the best and brightest students. While serving at Yangzhou, Shen's brilliance and dutiful character caught the attention of Zhang Chu (張蒭; 1015–1080), the Fiscal Intendant of the region. Shen made a lasting impression upon Zhang, who recommended Shen for a court appointment in the financial administration of the central court. Shen would also eventually marry Zhang's daughter, who became his second wife.