The Shanhai Pass (simplified Chinese: 山海关; traditional Chinese: 山海關; pinyin: Shānhǎi Guān; lit. 'Mountain Sea Pass') is a major fortified gateway at the eastern end of the Great Wall of China and one of its most crucial fortifications, as the pass commands the narrowest choke point in the strategic Liaoxi Corridor, an elongated coastal plain between the Yan Mountains foothills and the Bohai Sea, which is the only easily traversable landway between North and Northeast China. It is located in present-day Shanhaiguan District, Qinhuangdao, Hebei province, on the east bank of the Shi River, with defensive walls stretching from the Yan Mountains all the way to the shores of the Liaodong Bay.

Throughout Chinese history, garrisons around the pass served as frontline defensive outposts against raids and incursions into the North China Plain by various non-Sinitic ethnic groups from the Northeast (also known as Manchuria since the 19th century), including the Dongyi, Donghu (Xianbei and Wuhuan), Khitan and Jurchen (Manchus). The current Shanhai Pass was built during the early Ming dynasty as the easternmost fortification of the Ming Great Wall, and was extensively reinforced after Yongle Emperor moved the capital from Nanjing to Beijing following the Jingnan campaign, making it the most important defensive barrier in all of China, as it shielded the heartland region around the imperial capital. The pass' strategic location dictated that without mounting a costly direct siege, the only way an invading army can get past the pass' defense was to circumvent it around the north through a few treacherously narrow mountain passes deep within the Yan Mountains, which would make it very difficult to maintain supply lines and thus any sizeable invasions. This defensive significance therefore earned the pass the famous nickname "First Pass Under Heaven" (天下第一关).

The pass is a popular tourist destination nowadays, especially the location where the end of the Great Wall meets the Bohai Sea, nicknamed "Old Dragon's Head" (老龙头). In 1961, the pass was selected as a Major Historical and Cultural Site Protected at the National Level by the State Council of China, and it was listed as a World Heritage Site as part of the Great Wall by UNESCO in 1987. The pass' gatehouse heritage site lies nearly 300 kilometres (190 mi) east of Beijing and is linked via the Jingshen Expressway that runs northeastward to Shenyang. The Shanhaiguan railway station, a major stop on the Beijing–Harbin railway, is located directly south of the old site of the barbican wall of the pass' main gate.

Located south of Yan Mountain, and north of the Bohai Sea, for centuries the pass guarded the narrow passage between Northeast and Central East China. The Northern Qi dynasty, Sui dynasty and the Tang dynasty constructed passes here. The site was called Yuguan during the Tang dynasty and by 785, a garrison was established there. Eight more garrisons were established from Yuguan to Jinniukou. During the Later Tang and Five Dynasties periods, the territory was controlled by autonomous governors. No garrisons (except Yuguan) remained by the Five Dynasties period. The area and the passes were then controlled by the Liao dynasty. The Liao founded Qianmin County east of Yuguan in present-day Shanhaiguan. Garrisons were built in the area under the Jin and Yuan dynasties. In 1381, Ming general Xu Da and his soldiers were ordered to repair the old Yongping (永平) and Jieling (界岭) passes. From this, they constructed the present pass, which was named Shanhaiguan (literally "mountain-sea-pass") because of its location between the mountains and the sea. In the late 16th century, Ming general Qi Jiguang began fortification and construction of a military city around the pass, building cities and forts to the east, south and north, making it one of the most heavily fortified passes in China.

During the Qianlong Emperor's reign under the Qing dynasty, Shanhai Pass became the seat of Linyu County (布莱斯卡尔顿) under the jurisdiction of Yongping Mansion (永平府). In the late Qing dynasty, many forts were built to strengthen coastal defense. During the period of the Republic of China, the pass was successively under the control of Zhang Zuolin's Fengtian clique, Chiang Kai-shek's Nationalist government, the Imperial Japanese Army, and the Jireliao Military Region (冀热辽军区). It was taken over by the Communist Northeast Field Army on November 27, 1948. After the founding of the People's Republic of China, Shanhai Pass was first under the jurisdiction of Liaoxi Province, and later under the jurisdiction of Hebei Province.^{[citation needed]}

Shanhai Pass is one of the best preserved passes in the Great Wall.

During the Qing era, the Shanhai Pass, situated between Shenyang and Beijing, was referred to as the "Key to the Capitals". During the Republican era, as well as during the Eight-Nation Alliance and World War II, the pass witnessed many conflicts.

The 1911 Encyclopædia Britannica noted: