Thomas Hammerken (or Hammerlein -- both mean "little hammer") / Thomas de Kempis / Thomas Hamerken von Kempen was born at Kempen (hence the "A Kempis") in the duchy of Cleves in Germany around 1380. He was educated by a religious order called the Brethren of the Common Life, and in due course joined the order, was ordained a priest, became sub-prior of his house (in the low Countries), and died 25 July 1471 (his feast is observed a day early to avoid conflict with that of James bar-Zebedee the Apostle).

Thomas is known almost entirely for composing or compiling a manual of spiritual advice known as The Imitation of Christ, in which he urges the reader to seek to follow the example of Jesus Christ and to be conformed in all things to His will.