Dōgen Zenji (道元禅師; Japanese pronunciation: [doꜜː.ɡeɴ, -ŋeɴ], 26 January 1200 – 22 September 1253) was a Japanese Zen Buddhist monk, writer, poet, philosopher, and founder of the Sōtō school of Zen in Japan. He is also known as Dōgen Kigen (道元希玄), Eihei Dōgen (永平道元), Kōso Jōyō Daishi (高祖承陽大師), and Busshō Dentō Kokushi (仏性伝東国師).

Originally ordained as a monk in the Tendai School in Kyoto, he was ultimately dissatisfied with its teaching and traveled to China to seek out what he believed to be a more authentic Buddhism. He remained there for four years, finally training under Tiāntóng Rújìng, an eminent teacher of the Cáodòng lineage of Chinese Chan. Upon his return to Japan, he began promoting the practice of zazen (sitting meditation) through literary works such as Fukanzazengi and Bendōwa.

He eventually broke relations completely with the powerful Tendai School, and, after several years of likely friction between himself and the establishment, left Kyoto for the mountainous countryside where he founded the monastery Eihei-ji, which remains the head temple of the Sōtō school today.

Dōgen is known for his extensive writings like the Shōbōgenzō (Treasury of the True Dharma Eye, considered his magnum opus), the Eihei Kōroku (Extensive Record, a collection of his talks), the Eihei Shingi (the first Japanese Zen monastic code), along with his Japanese poetry, and commentaries. Dōgen's writings are one of the most important sources studied in the contemporary Sōtō Zen tradition.

Dōgen was probably born into a noble family, though as an illegitimate child of Minamoto Michichika. His foster father was his older brother Minamoto no Michitomo, who served in the imperial court as a high-ranking ashō (亞相; "Councillor of State"). His mother, named Ishi, the daughter of Matsudono Motofusa and a sister of the monk Ryōkan Hōgen, is said to have died when Dōgen was age 7.

In 1212, the spring of his thirteenth year, Dōgen fled the house of his uncle Matsudono Moroie and went to his uncle Ryōkan Hōgen at the foot of Mount Hiei, the headquarters of the Tendai school of Buddhism. Stating that his mother's death was the reason he wanted to become a monk, Ryōkan sent the young Dōgen to Jien, an abbot at Yokawa on Mount Hiei. According to the Kenzeiki (建撕記), he became possessed by a single question with regard to the Tendai doctrine:

As I study both the exoteric and the esoteric schools of Buddhism, they maintain that human beings are endowed with Dharma-nature by birth. If this is the case, why did the Buddhas of all ages — undoubtedly in possession of enlightenment — find it necessary to seek enlightenment and engage in spiritual practice?

This question was, in large part, prompted by the Tendai concept of original enlightenment (本覚 hongaku), which states that all human beings are enlightened by nature and that, consequently, any notion of achieving enlightenment through practice is fundamentally flawed.