Dieter Althaus (born 29 June 1958 in Heiligenstadt/Eichsfeld) is a German politician of the Christian Democratic Union (CDU). He served as the 3rd Minister President of Thuringia from 2003 to 2009. In 2003/04 he was the 58th President of the Bundesrat.

Althaus was a teacher for Physics and Mathematics at the Polytechnic Secondary School in Geismar, Thuringia, from 1983 to 1989, where he became deputy headteacher in 1987.

Since 1985 Althaus has been a member of the CDU, remaining with the party as it transformed itself from a loyal supporter of the GDR's ruling Socialist Unity Party of Germany (SED) to a loyal supporter of the West German party of the same name with which it merged in 1990 shortly after German reunification. In 2000 he became chairman of the CDU in Thuringia. Since 1990 he has been a member of the Thuringian Landtag.

In 1992 he became a member of Bernhard Vogel's cabinet as State Minister of Cultural Affairs and Education.

On 5 June 2003 Althaus was elected Minister President of Thuringia; he succeeded Bernhard Vogel, who had resigned for reasons of age. As Minister-President he served as President of the Bundesrat in 2003/04. Althaus was also part of the CDU/CSU team in the negotiations with the SPD on a coalition agreement following the 2005 federal elections,^[1] which paved the way to the formation of Chancellor Angela Merkel’s first government.

After the Thuringia elections of 2009, where the CDU went from having an absolute majority to not even having enough seats to form a majority coalition with the FDP, Althaus resigned as Minister-President and as chairman of the CDU in Thuringia.

Since 2010, Althaus has been working for Magna International.^[2]

Althaus was nominated by his party as delegate to the Federal Convention for the purpose of electing the President of Germany in 2022.^[3]

In 2006 Althaus spoke out in favour of a universal basic income.^[4]