Chan Siu-bak (陳少白) (20 July 1869 – 23 December 1934), born Chan Siu-man (陳紹聞), courtesy name Siu-bak (少白), art-named Kwai-shek (夔石), was a Chinese revolutionary from Sanwui, Kwangtung. He was one of the Four Bandits, together with Sun Yat-sen, Yau Lit and Yeung Hok-ling.
Chan was born to a family of Christian scholars, and entered a private school at the age of 6. When he was young, he learned about western knowledge from the translated books brought by his uncle Chan Mung-nam (陳夢南), a Christian preacher. In 1888, Chan became one of the first students to study at Christian College in China (格致書院) founded by Andrew P. Happer. He met Au Fung-Chi (區鳳墀), who introduced him to Sun Yat-sen, a medical student at Hong Kong College of Medicine for Chinese. Chan and Sun found revolution as a common interest between themselves.
With Sun's suggestion, Chan changed to study at Hong Kong College of Medicine for Chinese in January 1890. In Hong Kong, Sun introduced him to Yau Lit and Yeung Hok-ling. The four frequently met at Yeung Yiu Kee (楊耀記), Yeung's family shop at 24 Gough Street, to discuss a revolution against the Qing Dynasty, and were collectively called the Four Bandits by their neighbours. As Sun began his commitment to revolution upon graduation, Chan dropped out of the medical school to follow him.
In 1895, the Revive China Society in Hong Kong was founded by Sun, and Chan became a member of the society. Chan and Sun set up the headquarters of the society at 13 Staunton Street, Central, Hong Kong. Following the failure of the Canton Uprising of 1895, Chan fled to Yokohama, Japan with Sun and Cheng Si-leung. He would stay there for 2 years until he went to Taiwan to set up the Taiwan Chapter of Revive China Society.