Geertgen tot Sint Jans, also known as Geertgen van Haarlem, Gerrit van Haarlem, Gerrit Gerritsz, Gheertgen, Geerrit, Gheerrit, or any other diminutive form of Gerald, was an Early Netherlandish painter from the northern Low Countries in the Holy Roman Empire. No contemporary documentation of his life has been traced, and the earliest published account of his life and work is from 1604, in Karel van Mander's Schilder-boeck.

Het Schilder-Boeck or Schilderboek is a book written by the Flemish writer and painter Karel van Mander first published in 1604 in Haarlem in the Dutch Republic, where van Mander resided. The book is written in 17th-century Dutch and its title is commonly translated into English as 'The Book of Painters' or 'The Book of Painting' and sometimes as 'The Book on Picturing'. Het Schilder-Boeck consists of six parts and is considered one of the principal sources on the history of art and art theory in the 15th and 16th century Low Countries. The book was very well received and sold well. Karel van Mander died two years after its publication. A second posthumous edition, which included a brief, anonymous biography of van Mander was published in 1618. This second edition was translated by Hessel Miedema into English and published in 1994-1997 together with a facsimile of the original and five volumes of notes on the text.