Zen is a school of Mahayana Buddhism and originated in China during the 6th century CE as Chán. From China, Zen spread south to Vietnam, to Korea and east to Japan.

The word Zen is derived from the Japanese pronunciation of the Middle Chinese word 禪 Dzyen (Modern Mandarin: Chán), which in turn is derived from the Sanskrit word dhyāna, which can be approximately translated as "absorption" or "meditative state".

Zen emphasizes the attainment of enlightenment and the personal expression of direct insight in the Buddhist teachings. As such, it de-emphasizes mere knowledge of sutras and doctrine, and favors direct understanding through zazen and interaction with an accomplished teacher.

The teachings of Zen include various sources of Mahāyāna thought, especially Yogācāra, the Tathāgatagarbha Sutras and Huayan . The Prajñāpāramitā literature and, to a lesser extent, Madhyamaka have also been influential.

Traditionally the origin of Chán in China is credited to the Indian monk Bodhidharma. The story of his life, and of the Six Patriarchs, was constructed during the Tang Dynasty to lend credibility to the growing Chán-school.

Claude Anshin Thomas (born 1947) is an American Zen Buddhist monk and Vietnam War veteran. He is a vocal advocate of nonviolence and an international speaker, teacher and writer. Thomas was brought to Buddhism by Vietnamese Zen Buddhist teacher Thich Nhat Hanh, and was ordained in 1995 by Tetsugen Bernard Glassman of the Zen Peacemaker Order. Thomas brings Buddhist meditation practice and dharma teachings directly to the public through social projects, talks, and retreats. Since 1994, Thomas has walked 19,000 miles (31,000 km) on peace pilgrimages throughout Europe, Asia, the Middle East, and the United States. While walking, Thomas carries no money and begs for food and shelter in the mendicant monk tradition. He is the author of At Hell's Gate: A Soldier's Journey from War to Peace (2004) and founder of the Zaltho Foundation, a nonprofit organization dedicated to ending violence.