Sun Yat-sen (/ˈsʊnˈjɑːtˈsɛn/; 12 November 1866 – 12 March 1925) was a Chinese physician, revolutionary, statesman, and political philosopher who founded the Republic of China (ROC) and its first political party, the Kuomintang (KMT). As the paramount leader of the 1911 Revolution, Sun is credited with overthrowing the Qing dynasty and served as the first president of the Provisional Government of the Republic of China (1912) and as the inaugural premier of the Kuomintang.

Born to a peasant family in Guangdong, Sun was educated overseas in Hawaii and returned to China to graduate from medical school in Hong Kong. He led underground anti-Qing revolutionaries in South China, the United Kingdom, and Japan as one of the Four Bandits and rose to prominence as the founder of multiple resistance movements, including the Revive China Society and the Tongmenghui. He is considered one of the most important figures of modern China, and his political life campaigning against Manchu rule in favor of a Chinese republic featured constant struggles and frequent periods of exile.

After the success of the 1911 Revolution, Sun proclaimed the establishment of the Republic of China but had to relinquish the presidency to general Yuan Shikai who controlled the powerful Beiyang Army, ultimately going into exile in Japan. He later returned to launch a revolutionary government in southern China to challenge the warlords who controlled much of the country following Yuan's death in 1916. In 1923, Sun invited representatives of the Communist International to Guangzhou to reorganize the KMT and formed the First United Front with the Chinese Communist Party (CCP). He did not live to see his party unify the country under his successor, Chiang Kai-shek, in the Northern Expedition. While residing in Beijing, Sun died of gallbladder cancer in 1925.

Uniquely among 20th-century Chinese leaders, Sun is revered in both Taiwan (where he is officially the "Father of the Nation") and in the People's Republic of China (where he is officially the "Forerunner of the Revolution") for his instrumental role in ending Qing rule and overseeing the conclusion of the Chinese dynastic system. His political philosophy, known as the Three Principles of the People, sought to modernise China by advocating for nationalism, democracy, and the livelihood of the people in an ethnically harmonious union (Zhonghua minzu). The philosophy is commemorated as the National Anthem of the Republic of China, which Sun composed.

Sun's genealogical name was Sun Deming (Cantonese: Syūn Dāk-mìhng; 孫德明). As a child, his milk name was Tai Tseung (Dai-jeuhng; 帝象). In school, a teacher gave him the name Sun Wen (Syūn Màhn; 孫文), which was used by Sun for most of his life. Sun's courtesy name was Zaizhi (Jai-jī; 載之), and his baptized name was Rixin (Yaht-sān; 日新). While at school in British Hong Kong, he got the art name Yat-sen (逸仙; Yìxiān). Sun Zhongshan (Syūn Jūng-sāan; 孫中山, also romanized Chung Shan), the most popular of his Chinese names in China, is derived from his Japanese name Kikori Nakayama (中山樵; Nakayama Kikori), the pseudonym given to him by Tōten Miyazaki when he was in hiding in Japan. His birthplace city was renamed Zhongshan in his honour likely shortly after his death in 1925. Zhongshan is one of the few cities named after people in China and has remained the official name of the city during Communist rule.

Sun Deming was born on 12 November 1866 to Sun Dacheng and Madame Yang. His birthplace was the village of Cuiheng, Xiangshan County (now Zhongshan City), Canton Province (now Guangdong). He was of Hakka and Cantonese descent. His father owned very little land and worked as a tailor in Macau and as a journeyman and a porter. After finishing primary education and meeting childhood friend Lu Haodong, he moved to Honolulu in the Kingdom of Hawaii, where he lived a comfortable life of modest wealth supported by his elder brother Sun Mei.

During his stay in Honolulu, Sun began his education at the age of 10, attending secondary school in Hawaii. In 1878, after receiving a few years of local schooling, a 13-year-old Sun went to live with his elder brother Sun Mei, who would later make major contributions to overthrowing the Qing dynasty, and who financed Sun's attendance of the ʻIolani School. There, he studied English, British history, mathematics, science, and Christianity. Sun was initially unable to speak English, but quickly acquired it, received a prize for academic achievement from King Kalākaua, and graduated in 1882. He then attended Oahu College (now known as Punahou School) for one semester. By 1883, Sun's interest in Christianity had become deeply worrisome for his brother—who, seeing his conversion as inevitable, sent Sun back to China.

Upon returning to China, a 17-year-old Sun met with his childhood friend Lu Haodong at the Beiji Temple (北極殿) in Cuiheng, where villagers engaged in traditional folk healing and worshipped an effigy of the North Star God. Feeling contemptuous of these practices, Sun and Lu incurred the wrath of their fellow villagers by breaking the wooden idol; as a result, Sun's parents felt compelled to dispatch him to Hong Kong. In November 1883, Sun began attending the Diocesan Home and Orphanage on Eastern Street (now the Diocesan Boys' School), and from 15 April 1884 he attended The Government Central School on Gough Street (now Queen's College), until graduating in 1886.