Born at Reideburg, Saalkreis, near Halle, in what later became East Germany, he served in the Wehrmacht from 1943 to 1945 and briefly became an American and British prisoner of war. After World War II, he studied law and economics at the universities of Halle and Leipzig (1946-1949) and joined the East-German Liberal Democratic Party (LDPD) in 1946.
In 1965, he was elected to the Bundestag for the first time, a seat he would hold until 1998 (when he no longer ran for office). After serving in several party offices, he was appointed Minister of the Interior by Bundeskanzler Willy Brandt (SPD) in 1969; in 1974, he became Minister of Foreign Affairs (and Vice Chancellor), which he remained until he resigned in 1992 for health reasons. With these 18 years in office, he is frequently called the longest-serving Foreign Minister in the world.
In the SPD-FDP coalition, he helped shape Brandt's policy of deescalation with the communist east, commonly known as Ostpolitik, which was continued under Helmut Schmidt after Brandt's resignation in 1974.
Still, Genscher was one of the FDP's driving forces when, in 1982, the party switched sides from its coalition with the SPD to support the CDU/CSU in their Constructive Vote of No Confidence to have Helmut Schmidt replaced with Helmut Kohl as Bundeskanzler. Despite the great controversy that accompanied this switch, he remained of the most popular politicians in Germany.
He is mostly respected for his efforts that helped end the Cold War, to lead to German reunification, when, in eastern Europe, the communist government toppled; for example, he visited Poland to meet Lech Walesa as early as 1988. One event remembered by many is his September 30, 1989 speech from the balcony of the German embassy in Prague, in whose court yard thousands of East German citizens had assembled to flee to the west, when he announced that he had reached an agreement with the communist government that the refugees could leave. After the first few words, the speech drowned in cheers.
Since his resignation from all political activities in 1998, he has been active as a lawyer, in a public company, and in bona-fide international relations organizations. He founded his own Hans-Dietrich Genscher Consult GmbH in 2000.