Ancestor worship refers to rituals designed to commemorate and venerate the spirits of one’s deceased forebears. While it is often associated with the Confucian notion of filial piety, ancestor worship crosses the boundaries of religious traditions, geographical regions, and socioeconomic groups. Dating back to the Neolithic period, it is one of the oldest and most influential elements of Chinese religious culture. Sacrifices intended to pacify the spirits of the ancestors feature in Shang-dynasty oracle bone inscriptions, the oldest existing documents written in Chinese. These practices continued to flourish in early China, and the worship of imperial ancestors was eventually incorporated into the official state religion. When the organized religions of Buddhism and Daoism began to spread, new forms of ancestor worship rituals, such as the Buddhist Ghost Festival (yulanpen, 盂兰盆) and its Daoist equivalent (zhongyuan, 中元), began to flourish. By the end of the Song dynasty, following the Neo-Confucian reformation of domestic rituals, ancestor worship practices could be found at all echelons of Chinese society. In the early 21st century, these are performed in mainland China, Taiwan, and Hong Kong, and among overseas communities in Southeast Asia and North America. These rituals can be divided into several types: (1) the worship of individual-lineage ancestors, which entails the presentation of ritual offering to their tablets or images at the household altar, (2) the collective veneration of ancestors and, most importantly, the founder of the lineage, at the ancestral hall, and finally, (3) communal rituals dedicated to the worship of the ancestors, which also take place at the grave on specific dates, such as the Qingming (清明) and Double Ninth (Chongyang, 重陽) Gravesweeping Festivals. Given its longevity and cultural prominence, the cult of the ancestors has attracted the attention of scholars in Chinese studies. Following the earliest accounts of ancestor worship practices written by Christian missionaries, most of the work during the 20th century was produced by anthropologists, who situated ancestor worship in the larger context of the kinship system and lineage organization. Late 20th- and early-21st-centuries scholarship has sought to expand these seminal studies: archaeologists and art historians offer an analysis of the material objects associated with the cult of the ancestors, historians draw on textual sources to explore its different manifestations and sociocultural implications, and ethnographers offer new accounts of the varieties of ancestor worship practices among ethnic minorities groups in the mainland and overseas Chinese communities across the globe.