Fazang (Chinese: 法藏; pinyin: Fǎzàng; Wade–Giles: Fa-tsang; 643–712) was a Sogdian-Chinese Buddhist scholar, translator, and religious leader of the Tang dynasty. He was the third patriarch of the Huayan school of East Asian Buddhism, a key figure at the Chinese Imperial Court, and an influential Chinese Buddhist philosopher. Some scholars see him as the main figure in or even de facto founder of the Huayan school. Fazang's ancestors came from the Central Asian region of Sogdia, a major center for Silk Road trade, but he was born in the Tang capital of Chang'an (now Xi'an), where his family had become culturally Chinese.

Fazang was known for his skill as a translator, knowledge of Sanskrit, and for his efforts to produce a new translation of an extended edition of the Gaṇḍavyūha sūtra. He also composed an original commentary on the Avatamsaka Sutra, called the Huayan jing tanxuan ji (Record of Investigating the Mystery of the Huayan jing). He was also known as a popularizer and promoter of Huayan teachings, through his relationship with Empress Wu Zeitian and his authorship of several essays on Huayan philosophy, especially Essay on the Golden Lion.

Although there remains ambiguity with varying interpretations of biographical sources, most recent scholarship promotes that the well-known name Fazang is not only the monk's dharma-name, but the secular name he used prior to being ordained. His surname was Kang, which originated from his place of birth, Kangjuguo. Furthermore, he had the nickname of Xianshou 賢首 which appears to have been the style-name given to him by his parents, despite prior claims that it was an honorific title from Empress Wu. This is further supported by Fazang's self-reference using the nickname, which strongly suggests it was not an honorific title as previous scholars thought. His title as a teacher and of distinction (biéhào 別號) was Dharma Master Guoyi 國一法師, in which his disciples referred to him post-ordination and in the latter stages of his life.

Little is known about Fazang's early life. Fazang's family were Sogdians and lived in an ethnically Sogdian enclave in the imperial capital of Chang’an. Fazang's father, Kang Mi, held an official title in the Tang court. Not much was known about his mother, although Chinese biographies state that she became pregnant "after dreaming of swallowing rays of sunshine". Accounts of the affluence of Fazang's grandfather hint at his father's ability to attain higher up positions in Tang aristocratic circles, despite being a Sogdian immigrant. However, epigraphic and textual sources show an abundance of ambiguity regarding his family.

In contrast to the uncertainty surrounding his blood relatives, Fazang's dharma family is better recorded in the sources. Zhiyan was his primary teacher, while Fazang's fellow scholars, Daocheng and Baochen, exerted additional influence. Fazang also had a multitude of fellow-disciples, although sources only record four primary names: Huixiao, Huaiji, Huizhao, and most famously, Uisang, who went on to establish Hwaeom Buddhism in Korea. It is argued that he had many other disciples, a nun-disciple Facheng, two Korean disciples in addition to Uisang, and finally a Chinese biographer, Qianli.

Fazang had an early interest in Buddhism. When he turned fifteen, he set his finger on fire in front of a “Ayuwang shelita” (a Famensi pagoda enshrining the finger bone of the Buddha). This was a popular religious practice at the time. Fazang became disappointed in his initial search for a proper teacher in the capital, and so he went to Mount Zhongnan, where he studied Mahayana sutras, like the Avatamsaka sutra and also engaged in Daoist practices of consuming herbal elixirs.

After several years of seclusion and hearing his parents were ill, Fazang returned to Chang’an and eventually met his first teacher Zhiyan, after impressing him with his knowledge of the Avatamsaka. He began his lay discipleship with Zhiyan in roughly 663; however, Fazang did extensive traveling and did not remain with his teacher consistently. Before Zhiyan's passing in 668, he instructed his two vinaya masters, Daocheng and Baochen, to care for Fazang. Daocheng was appointed as one of the three principals of the newly constructed monastery in Chang’an, Taiyuansi. This would be where Fazang would enter Buddhist priesthood for the remainder of his life. Previous biographical sources claim that Fazang was either overqualified for the bodhisattva-precepts or had his ordination situated in a miraculous context, yet both were distorted accounts attempting to validate the lack of evidence Fazang ever had a full ordination.

After 670 and Fazang's monastic ordination, he spent time travelling between Mount Zhongnan (staying at Wuzhensi and Zhixiangsi) and Taiyuansi in the capital. He often lectured on the Avatamsaka sutra.129 From 680 to 687, Fazang began working with the Indian monk Divākara on translating Indian texts into Chinese.