Dr. (jur.) Guido Westerwelle (*December 27, 1961) is a German politician and leader of the Free Democratic Party of Germany (FDP).

Guido Westerelle was born in Bad Honnef in Germany. Since 1980 he is a member of the FDP. He was also a founding member of Junge Liberale, the youth organisation of the FDP, and their chairman 1983–1988. Since 1988 he is member of the Executive Board of the FDP. In 1994 he was appointed General Secretary of FDP, in 1996 elected to Bundestag (the German parliament), and in the elections of September 2002, he was FDP's chancellor-candidate.

On July 20, 2004, he attended conservative leader Angela Merkel's 50th birthday party accompanied by his male partner, Cologne businessman Michael Mronz, for the first time at an official gathering, making it evident that he no longer expected his relationship with Mronz to be treated discretely. Westerwelle effectively came out in public as a homosexual, however causing markedly less sensation than recent coming outs by leading politicians in Western Europe, such as the popular heads of government in the states of Berlin (Wowereit), Hamburg (Ole von Beust) and Peter Mandelson in Britain or Bertrand Delanoë, the mayor of Paris.

That is not to say that the sexual orientation of leading politicians is a totally uncharged topic. Westerwelle's main opponent in FDP, the late Jürgen Möllemann, hinted that the then-unreveiled sexual leanings could pose a security risk, alleging that Westerwelle was "excessively pro-Israel" because Mossad should have acquired compromising evidence of his private life. Although this debate within FDP was carried out in the language of anti-semitism versus uncritical support of Israel's suppression of the Palestinians, it was also connected to the party's stance on Gay rights issues.

For Germany's future politics, it may be relevant that the southern Catholic Conservative electorate, that of the Bavarian CSU, risks to get allienated if, as is likely, they are asked to vote for a female Hamburg-born Lutheran ex-East German Angela Merkel for Chancellor with a homosexual liberal Westerwelle, from westernmost Germany, as her foreign minister candidate.