Theodore Hamberg (Chinese: 韓山明 or 韓山文), was a Swedish missionary and author active in China. He is known for his role in having authored an important account on the early Taiping rebellion and for his role in establishing Christian missions in Guangdong province. He also laid the foundations for the study of the Hakka dialect in the West. He is the younger brother of the Swedish chemist Nils Peter Hamberg.
Hamberg was the son of a sea captain and worked as a businessman, after graduating from school. In 1844, he left his trade to join the Basel Mission and spent the following two years in training at a missions school in Switzerland.
In 1846, Hamberg was sent to China, where he arrived on March 19 the following year and started to work in the Guangdong mission, where he worked to convert members from the Hakka community. He also worked out a draft of the first description of the Hakka dialect, which provided the foundation to D. MacIver's Hakka dictionary. Hamberg initially worked under the influential German missionary Karl Gützlaff, but Hamberg gradually grew skeptical of Gützlaff's strategy of mass conversions; instead he advocated a more cautious approach, which in due course would bring him into conflict with Gützlaff and with the Basel Mission. After the death of Gützlaff, Hamberg was vindicated and he continued to work under the Basel Mission.
In 1852, Hamberg met Hong Xiuquan's cousin Hong Ren'gan, who had been separated from the rebellion and fled to Hong Kong. Hong Ren'gan also provided Hamberg with important information on the Taiping rebellion, which formed the basis of a book Hamberg later published on the rebellion. The book was the first extensive account on the Taiping rebellion in a Western language and remains an important source on the early life of Hong Xiuquan.