Tib., dag po: Without Error
One of the two original impulses that led up to the Kagyud-pa tradition, this school is named after its founder Dagpo Lharje Gampopa (1079-1153). The school, one of the Eight Practice Lineages, is sometimes called Marpa Kagyud in honor of the man who inspired (not "founded") this lineage of teachings. Having combined the teachings of Naropa as found in the Naro-chos-drug with the Mahamudra teachings of Milarepa, Gampopa founded his tradition in 1125.
Although Dagpo constitutes, brought forth, and contains most of the schools that make up the Kagyudpa tradition, in historical terms it was preceded by the Shangpa (established in 1057), the other lineage that led to the formation of the Kagyudpa as a whole.
Among those inspired by Gampopa and his synthesis were many inventive and non-conformist monks and masters, and their activities and teachings led to a variety of subdivisions. Four such schools were founded by his direct students, and are collectively known as the The Four Golden Lineages - sometimes simply as "the four major schools"
Of these, both the Karmapa and Phagmo Drupa have developed once more into several subivisions each (see historical overview).