Thomas Fincke (6 January 1561 – 24 April 1656) was a Danish mathematician and physicist, and a professor at the University of Copenhagen for more than 60 years.
Thomas Jacobsen Fincke was born in Flensburg in Schleswig. Fincke was the son of Councillor Jacob Fincke and Anna Thorsmede. He completed his primary schooling at Flensburg. From 1577, he studied mathematics, rhetoric and other philosophical studies for five years at the University of Strasbourg.
Fincke's lasting achievement is found in his book Geometria rotundi (1583), in which he introduced the modern names of the trigonometric functions tangent and secant. In 1590, he became professor of mathematics at the University of Copenhagen. In 1603 he also obtained a professorship in medicine.
He was married to Ivaria Jungesdatter Ivers (1574-1614). His son Jacob Fincke (1592-1663) was a professor of physics. His daughters married scientist Caspar Bartholin the Elder (1585–1629), botanist Jørgen Fuiren (1581-1628), historian Ole Worm (1588-1654) and theologian Hans Brochmand (1594-1630). 
Fincke died at Copenhagen and was buried at Vor Frue Kirke.
- ^ "Fincke, Thomas, 1561-1656". Dansk biografisk Lexikon. Retrieved August 1, 2019.
- ^ Jørgen Fuiren Dansk Biografisk Leksikon Retrieved December 1, 2020
- ^ "Worm, Ole (Oluf), 1588-1654". Dansk biografisk Lexikon. Retrieved August 1, 2019.
- ^ Hans Brochmand - teolog Dansk Biografisk Leksikon Retrieved December 1, 2020
- O'Connor, John J.; Robertson, Edmund F., "Thomas Fincke", MacTutor History of Mathematics archive, University of St Andrews
- 1561 births
- 1656 deaths
- 16th-century Danish scientists
- 17th-century Danish scientists
- 16th-century Danish mathematicians
- 17th-century Danish mathematicians
- Danish mathematicians
- Danish physicists
- Science teachers
- Mathematics writers
- University of Strasbourg alumni
- Academic staff of the University of Copenhagen
- Rectors of the University of Copenhagen
- People from Flensburg
- Burials at the Church of Our Lady, Copenhagen
- Danish scientist stubs
- European mathematician stubs