German centre-right political party that supports a free-market economy and social welfare programs but is conservative on social issues. The CDU has also been a strong advocate of European integration and has cultivated close relations with the United States while in government. The CDU, along with its Bavarian affiliate, the Christian Social Union (CSU), emerged out of the ashes of the Third Reich to become Germany's most successful political party, governing the Federal Republic of Germany for the first two decades after its founding and for most of the last two decades of the 20th century.

The CDU was founded in 1945 by a diverse group of former Weimar Republic (1919–33) politicians, including activists in the old Roman Catholic Centre Party, liberal and conservative Protestants, workers, intellectuals, and segments of the middle class who decided to become active in the new postwar democracy in order to prevent any rebirth of fascism in Germany. Indeed, Nazi Germany was very much on the minds of these early Christian Democrats, and, despite the disparate backgrounds of the party's leaders and members, they shared some critical core beliefs that have shaped and guided the party since its founding.

First, they believed that the historic conflicts and divisions between Roman Catholics and Protestants were in part responsible for the rise of Adolf Hitler (Hitler, Adolf). The major thrust of Catholic political activity, for example, was directed through the Centre Party, while Protestants tended to support the various nationalist and liberal parties; Catholics generally endorsed the concordat between the Vatican and Hitler (1933), thus undercutting any substantial opposition to the regime by Catholic political activists. To ensure that such a regime could not usurp democratic institutions again, the founders of both the CDU and the CSU were determined to create parties that contained adherents of both groups; since the CDU's founding, great emphasis has been placed on ensuring a balance of religions within the party's various organizations. The task of ending the historic enmity between Roman Catholics and Protestants was made easier by the fact that the division of Germany into West and East Germany had brought rough parity between the two denominations within the Federal Republic.

Second, after some initial flirtation with socialism (particularly because of links with members in the Soviet zone before Germany was divided into two countries), most Christian Democrats by the end of the 1940s had reached a consensus that a “social market economy”—a mix of free-market capitalism with strong government regulation and a comprehensive welfare state—was the best alternative for Germany.

Third, the party's foreign policy was staunchly anticommunist, pro-American, and supportive of European integration; indeed, West Germany was pivotal in the creation of the European Coal and Steel Community (1952), one of the precursors of the European Union (EU).

The CDU-CSU alliance won stunning victories in Germany's elections in 1949 and in subsequent elections in the 1950s. It owed its early success largely to two men: Konrad Adenauer (Adenauer, Konrad), the party's first leader and German chancellor from 1949 to 1963, and Ludwig Erhard (Erhard, Ludwig), considered the father of Germany's Wirtschaftswunder (“economic miracle”), who served as Adenauer's economics minister and then succeeded him as chancellor in 1963.

The CDU-CSU was so successful in Germany's early post-World War II elections that by the end of the 1950s it had transformed the party system. Almost all of the small, regional splinter parties that had competed with the CDU-CSU in 1949 had by 1957 been absorbed, and, more importantly, the alliance's victories had by 1959 caused the major opposition party, the Social Democratic Party (Social Democratic Party of Germany) (SPD), to fundamentally revise its program, leadership, and organization. By the 1960s, however, the CDU-CSU's long tenure in office and Adenauer's advancing age had begun to take their toll. Whereas in 1957 the CDU-CSU captured a majority of the votes cast, in 1961 they slipped to 45.4 percent as the reformed and revitalized SPD finally reversed its electoral decline.

In 1963, at age 87, Adenauer stepped down as chancellor and was replaced by Erhard, who was unable to transfer his success as economics minister to the chancellorship. Unlike Adenauer, Erhard had no strong base of support in the party. In 1965, when the country experienced its first recession, several ambitious challengers questioned his leadership abilities. In 1966, when the Free Democratic Party (FDP), the CDU-CSU's coalition partner, withdrew its support over how to handle the recession, Erhard's government collapsed. The CDU-CSU then agreed to join a grand coalition with the SPD and thus was able to hold onto a share of power (and control the office of chancellor) until 1969.

After the 1969 election the CDU-CSU went into opposition. Although they still combined to form the largest faction in the Bundestag, they were unable to find a coalition partner and were outnumbered by the combined totals of the SPD and FDP. After 20 years in power, the CDU was badly in need of reform and renewal; it was without a leader, a modern organization, and an attractive program.

For its first 20 years the party had a very weak organization and was essentially run out of the chancellor's office. From 1973, when Helmut Kohl (Kohl, Helmut) was elected leader, the CDU developed a strong organization. For example, full-time staff in local and regional party offices was increased, and at the national level Kohl recruited young campaign strategists who applied new communication techniques to the party's electioneering efforts. Kohl's efforts also increased the party's membership levels, which rose from 300,000 in the 1970s to nearly 700,000 by the mid-1990s. It lost the elections of 1976 and 1980 to the SPD and its coalition partner, the FDP, but returned to power in 1982, when the FDP switched allegiances and helped elect Kohl chancellor. He subsequently won four successive national elections and held the chancellorship for a record 16 years. During his tenure in office, Kohl engineered the reunification of Germany and was pivotal in the creation of the euro, the EU's single currency, which was finally introduced after he left office.

In 1998 the CDU-CSU suffered one of the worst defeats in their history. After more than a decade and a half of the same government and with the economy suffering from recession as a result of the enormous costs associated with unification, many German voters wanted a change and, above all, a new chancellor. Over the next year, the party was embroiled in a major finance scandal, which involved illegal fund-raising by Kohl and his deputies. As a result, Kohl's successor as party leader, Wolfgang Schäuble, was forced to resign, and the party subsequently elected as its leader someone who was untainted by the scandal—Angela Merkel (Merkel, Angela), a former East German and the first woman to head a major German party. In 2005, under Merkel's leadership, the CDU-CSU bloc edged out the SPD to become the largest party in the Bundestag. With the smaller parties unable or unwilling to provide the CDU-CSU with the needed margin to govern, Merkel entered into a grand coalition with the SPD, thus taking power as Germany's first woman chancellor.

From its beginnings, the CDU has emphasized that it is a Volkspartei (“people's party”) that has offered a political home to all Germans—regardless of religion, region, social class, occupation, gender, or age—who accept its overarching principles. As the archetypal “catchall party” that is pragmatic and office-seeking and that views itself as representing the entire population rather than particular sectional interests, the CDU has been remarkably open to a wide variety of political interests: both big and small businesses, labour and agriculture, and small towns and big cities are all represented within its ranks.

The party's organization is decentralized. The various Land (state), district, county, and local organizations, together with auxiliary women's, youth, business, agricultural, and labour groups, are independent of any national or central control (though, since unification, the former East German party organizations have been more dependent on central control than their Western counterparts). Indeed, the key to the party's success at the national level has been its ability to mobilize the support of these subnational and auxiliary groups. For example, Kohl's record 25-year tenure as the party's national leader was largely the result of the personal relationships that he had developed with subnational leaders and his detailed knowledge of local conditions.