Ren Zhu (Chinese: 任柱; died 1867), born in Mengcheng Anhui, China, was an eminent military leader of the Nien Rebellion who was known during his military tenure as the King of Lu (魯王). He led Nien (捻軍) forces to many military victories. Li Hongzhang praised Ren Zhu's ability to command hundreds of thousands of cavalry. In May 1865, during a campaign against the Qing in Shandong, he shot the Qing general Sengge Rinchen during the Battle of Gaolouzhai, which sent a shock to the Qing Dynasty and resulted in the promotion of field marshal Zeng Guofan to commander of the Huai Army, Li Hongzhang.

In June 1865, he with Lai Wenguang, he commanded the Nien cavalry forces numbering 90,000 in surrounding and attacking the capital of Beijing, which was nearly successful. He died in battle in Ganyu, killed by the Qing dynasty general Liu Mingchuan.