Osahito (統仁; 22 July 1831 – 30 January 1867), posthumously honored as Emperor Kōmei (孝明天皇, Kōmei-tennō), was the 121st emperor of Japan, according to the traditional order of succession. Kōmei's reign spanned the years from 1846 through 1867, corresponding to the final years of the Edo period.

During his reign there was much internal turmoil as a result of Japan's first major contact with the United States, which occurred under Matthew C. Perry in 1853 and 1854, and the subsequent forced re-opening of Japan to Western nations, ending a 220-year period of national seclusion. Emperor Kōmei did not care much for anything foreign, and he opposed opening Japan to Western powers. His reign would continue to be dominated by insurrection and partisan conflicts, eventually culminating shortly after his death in the collapse of the Tokugawa shogunate and the Meiji Restoration in the beginning of the reign of his son and successor Emperor Meiji.

Before Kōmei's accession to the Chrysanthemum Throne, his personal name (imina) was Osahito (統仁) and his title was Hiro-no-miya (煕宮). Osahito was born on 22 July 1831 and was the fourth son of Emperor Ninkō and his consort Ōgimachi Naoko (正親町雅子). Osahito's Imperial Family lived with him in the Dairi of the Heian Palace.^{[citation needed]}

Prince Osahito was enthroned as Emperor on 10 March 1846 upon the death of his father. The succession was considered to have been received by the new monarch; and shortly thereafter, Emperor Kōmei is said to have acceded the throne. The years of Kōmei's reign correspond with a period in which Tokugawa Ieyoshi, Tokugawa Iesada, Tokugawa Iemochi, and Tokugawa Yoshinobu were leaders at the pinnacle of the Tokugawa shogunate. On 8 July 1853 US Commodore Matthew Perry arrived with his "Black Ships" to force trade with Japan. The Tokugawa shogunate, which had controlled military and civil affairs in Japan's feudal provinces for some three centuries, proved unable to meet the new challenge of open trade with the West. At the time, Emperor Kōmei still retained only symbolic power at his court in Kyoto. As the shogunate, divided by internal disputes, gradually surrendered sovereignty to the foreign powers under threat of military force, Emperor Kōmei began to assert himself and regain many of the powers his ancestors had conceded to the Tokugawa clan at the close of the Sengoku ("warring states") period. The Emperor's younger sister, Imperial princess Kazu-no-Miya Chikako (和宮親子内親王), was married to the Tokugawa shōgun Tokugawa Iemochi as part of the Movement to Unite Court and Bakufu. Both the Emperor and his sister were against the marriage, even though he realized the gains to be had from such familial connections with the true ruler of Japan. Emperor Kōmei did not care much for anything foreign, and he opposed opening Japan to Western powers, even as the shogun continued to accept foreign demands.

On 22 January 1858, Daigaku-no-kami Hayashi Akira headed the bakufu delegation which sought advice from Emperor Kōmei in deciding how to deal with newly assertive foreign powers. This would have been the first time the Emperor's counsel was actively sought since the establishment of the Tokugawa shogunate. The most easily identified consequence of this transitional overture would be the increased numbers of messengers streaming back and forth between Edo and Kyoto during the next decade. Concerning these difficult Imperial audiences in Kyoto, it is somewhat remarkable that the shogun and his bakufu were represented by Hayashi Akira, a 19th-century neo-Confucian scholar/bureaucrat who might have been somewhat surprised to find himself at a crucial nexus of managing political change—moving arguably "by the book" through uncharted waters with well-settled theories and history as the only reliable guide. Hayashi Akira was dispatched from Edo to Kyoto in October 1858 to explain the terms of the Treaty of Amity and Commerce (日米修好通商条約, Nichibei Shūkō Tsūshō Jōyaku), also known as the Harris Treaty. Hayashi's twofold task was to both explain the terms to a sceptical Emperor and gain the sovereign's assent to it. Kōmei did ultimately acquiesce in February 1859 when he came to understand that there was no alternative.

The pilgrimage of the 14th shogun Tokugawa Iemochi to Kyoto in 1863 was a defining moment not only in 19th century relations between the military bakufu and the Imperial Court, but also in what history would come to call the Meiji Restoration. The reception by Emperor Kōmei of the shogun in the Kyoto palace can be seen as a moment at which the political realm was thoroughly redefined, becoming a transitional imperial realm. This impression was enforced by the ensuing pilgrimage by Emperor Kōmei to the Kamo shrine, with the shogun in tow. This public demonstration showed that a new order had now emerged in the realm.

After reluctantly accepting the Harris Treaty, Japan quickly signed similar treaties, called the Ansei Treaties (also known as the Ansei Five-Power Treaties, with Russia, France, Great Britain, and the Netherlands). The treaties stipulated that the citizens of those foreign nations would be allowed to reside and trade at will in the cities of Edo, Nagasaki, Niigata, Kobe and Yokohama. Those five cities were to be opened to foreign trade with the four Western nations in the treaties. In addition, the treaties stipulated that a system of extraterritoriality would provide for the subjugation of foreign residents to the laws of their own consular courts instead of the Japanese legal system.

Emperor Kōmei was infuriated with nearly every development during his reign as Emperor, and during his lifetime he never saw any foreigners nor did he know much about them. Unequal trade treaties with the Western powers, such as the Treaty of Kanagawa and the Harris Treaty were signed without Imperial sanction and in spite of the Emperor's refusal to approve them. He twice expressed his will to abdicate in protest. During his reign he started to gain more power as the Tokugawa shogunate declined, though this was limited to consultation and other forms of deference according to protocol. Emperor Kōmei generally agreed with anti-Western sentiments, and, breaking with centuries of imperial tradition, began to take an active role in matters of state. As opportunities arose, he fulminated against the treaties and attempted to interfere in the shogunal succession. His efforts culminated in 1863 with his "Order to expel barbarians". Although the Shogunate had no intention of enforcing the order, it nevertheless inspired attacks against the Shogunate itself and against foreigners in Japan: the most famous incident was the killing of British trader Charles Lennox Richardson, for which the Tokugawa government paid an indemnity of 100,000 pound sterling. Other incidents included the bombardments of Shimonoseki and Kagoshima, and the destruction of Japanese warships, coastal guns, and assorted military infrastructure throughout the country. These incidents showed that Japan could not match the military might of the Western powers at the time, and that military confrontation could not prove to be a diplomatic solution.