Ingrid Matthäus-Maier was born on September 9, 1945, in Werlte. In 1965 she graduated from high school in Duisburg. She studied law in Giessen and Münster, and then worked as an administrative Law judge in Münster until 1976. She joined the FDP (Free Democratic Party) in 1969. In 1972 she became federal chairwoman of the Junge Demokraten (the FDP's youth organization). After the change of coalition in 1982 ("spiritual-moral change") she left the FDP and joined the SPD (Social Democratic Party). She was a member of the German parliament from 1976 to 1982 and from 1983 to 1999. From 1999 to 2008 she was chairwoman of the Kreditanstalt für Wiederaufbau (KfW - Reconstruction Credit Institute), from 2006 to mid-2008 she was chairwoman and spokeswoman of the KfW Bankengruppe (resigned in April 2008). Since 2007 Ingrid Matthäus-Maier has been a member of the Naturallianz (Nature Alliance), which was founded by Federal Minister Sigmar Gabriel and is committed to the preservation of biological diversity.

"Red Ingrid", as she was sometimes labelled by journalists, was crucially involved in the formulation of the 1974 FDP church paper "Freie Kirche im Freien Staat" ("Free Church in the Free State") - which was amazingly progressive at the time and also today - which called for a clear separation of state and church (including the abolition of church tax and the replacement of all exclusive state payments to the Churches). In 1998 she was awarded the CICERO Speaker's Prize.