Ziesar (German pronunciation: [tsiˈeːzaʁ] ) is a town in the Potsdam-Mittelmark district, in Brandenburg, Germany. It is situated 24 km (15 mi) south-west of the city of Brandenburg.

Ziesar: Population development
within the current boundaries (2013)

Year Pop. ±% p.a. 1875 3,590 —     1890 3,619 +0.05% 1910 3,708 +0.12% 1925 3,757 +0.09% 1933 3,670 −0.29% 1939 3,879 +0.93% 1946 4,964 +3.59% 1950 5,057 +0.47% 1964 4,096 −1.49% 1971 3,677 −1.53% 1981 3,390 −0.81% 1985 3,345 −0.33% 1989 3,266 −0.60% 1990 3,219 −1.44% 1991 3,149 −2.17% 1992 3,110 −1.24% 1993 3,090 −0.64% 1994 3,064 −0.84% 1995 3,028 −1.17% 1996 3,012 −0.53%

Year Pop. ±% p.a. 1997 3,010 −0.07% 1998 3,031 +0.70% 1999 3,006 −0.82% 2000 2,984 −0.73% 2001 2,930 −1.81% 2002 2,910 −0.68% 2003 2,893 −0.58% 2004 2,860 −1.14% 2005 2,806 −1.89% 2006 2,763 −1.53% 2007 2,716 −1.70% 2008 2,657 −2.17% 2009 2,605 −1.96% 2010 2,553 −2.00% 2011 2,485 −2.66% 2012 2,482 −0.12% 2013 2,453 −1.17% 2014 2,441 −0.49% 2015 2,451 +0.41% 2016 2,444 −0.29%

Following local elections held on 26 May 2019:

• SPD 5 seats
• CDU 4 seats
• Freie Bürger und Bauern (FBB) (Free citizens and farmers) 3 seats

During the Cold War the Western Allies considered Ziesar, specifically Exit 76 from Autobahn 2, the halfway point of the transit route between West Berlin and "mainland" West Germany. Road patrols offering breakdown services and assistance with DDR and Soviet authorities to Allied travelers were provided by Americans based in Berlin east of Ziesar and by the British detachment at Helmstedt west of it.

• Johannes Aepinus (1499-1553), theologian and church reformer
• Paul Schneider (1863-1946), the secret war councilor, farmer and the last private owner of Castle Ziesar from 1917 to 1945

• Wilhelm Kuhnert (1865-1926), painter