Zhu is the pinyin romanization of five Chinese surnames: 朱, 祝, 竺, 猪 and 諸.

The most prominent of the five, Zhu (朱), is the 17th name in the Hundred Family Surnames poem and was the surname of the Ming dynasty emperors. It is alternatively spelled Chu (primarily in Hong Kong, Macau and Taiwan), Gee^{[citation needed][clarification needed]} in the United States & Canada, and Choo (mostly in Singapore and Malaysia). As of 2018, it is the 14th most common surname in the People's Republic of China, with a population of around 18 million.^[1][2][3]

One interpretation is that 朱 refers to 朱雀 meaning vermillion. This is a completely different character from another Chu (楚), which is less common than Zhu.

The ancestral surname (姓) of the ruling family of the State of Zhu (邾) was Cao. (p. 144, Xueqin). The State of Zou, as it was later renamed, was conquered and annexed by the state of Chu during the reign of King Xuan of Chu (369–340 BC). (p. 43, Chao). The ruling family and its descendants adopted Zhu (朱) as their surname in memory of their former state of Zhu (邾). (p. 43, Chao & p. 239, Tan).

During the Ming dynasty, some people of the Zhu clan moved to Taiwan, and others later migrated to Southeast Asia, Europe and the Americas. During the Qing dynasty the House of Zhu was purged by the House of Aisin-Gioro and the Manchu people who led the Qing armies. Many royal family members of the House of Zhu were executed at Caishikou Execution Grounds during the Qing dynasty. The Zhu clan is also found in Korea and is known as 주 (朱; Ju, Joo); it is the 32nd most common name in Korea though it is combined with the Zhou (周) surname (see List of Korean surnames).

Zhu (朱) is technically a branch of the Cao (曹) surname. Nowadays, Zhu is 14th most common, while Cao is 27th most common in terms of population size.^[4]

A 2013 study found that it was the 14th most common surnames, shared by 17,000,000 people or 1.280% of the population, with the province with the most being Jiangsu.

• Zhu (state)
• House of Zhu