Eugen Karl Albrecht Gerstenmaier (25 August 1906 – 13 March 1986) was a German Protestant theologian, resistance fighter in the Third Reich, and a CDU politician.

After training as a salesman, Gerstenmaier did his Abitur and then studied philosophy, German language and literature, and Protestant theology in Tübingen, Rostock and Zurich.

This by the standards of "hanging judge" Roland Freisler unusually lenient sentence (the prosecution had demanded death by hanging) may partially be explained by Gerstenmaier's playing the "unworldly theologian" role to the hilt, partially by intercession on his behalf with Freisler by acting national press chief Helmut Sündermann.

On 31 January 1969, Gerstenmaier resigned his post as Bundestag President after public controversy about claims of certain compensation benefits, to which he was legally entitled.

Eugen Gerstenmaier belonged to a CDU faction who internally criticized Konrad Adenauer's policy of engaging the West because that brought along with it a tendency to turn away from the goal of reuniting Germany.

Even in social policy, Gerstenmaier was rather critical of Adenauer and supported Ludwig Erhard's position instead, with pointedly Christian-Protestant arguments against the "total welfare state".