Tiedemann Giese (1 June 1480 – 23 October 1550), was Bishop of Kulm (Chełmno) first canon, later Prince-Bishop of Warmia (Ermland) whose interest in mathematics, astronomy, and theology led him to mentor a number of important young scholars, including Copernicus.

[2] At the age of 12 years, Tiedemann, along with his cousin, Johann Ferber, entered the University of Leipzig, and subsequently studied at Basel and in Italy.

[8] Bishop Giese was a lifelong friend and frequent companion of the astronomer and proponent of heliocentrism Nicolaus Copernicus[9] and shared his interest in astronomy.

[13] The mathematician, Rheticus, published a list of Giese's astronomical instruments, which he considered to have been made by men who really understood their mathematics.

[11] Giese actively encouraged his friend, Copernicus, to publish his findings in relation to the movement of the planets in the solar system.

The region's ethnic German inhabitants resisted full incorporation into Poland, but turned to the Polish King for support against the Teutonic aggressors.

Nicolaus Copernicus explained that his "devoted friend, Tiedeman Giese, [was] a man filled with the greatest zeal for the divine and the liberal arts.

In the preface of his book, De revolutionibus, Copernicus credits Giese with encouraging publication and urging him not to conceal the principles on which he deduced his theory of planetary motions.

[22] Among his known publications is Centum et decem assertiones, quas auctor earum Flosculos appellavit de homine interiore et exteriore and Antilogikon, a polemical refutation of Lutheran reformer Johann Briesmann.

[citation needed] His friend, Copernicus (who died in 1543) willed his writings to Giese and left his library to the church administration of the Prince-Bishopric of Ermland (Warmia).