Population censuses have been conducted for thousands of years and they are one of the bases of any official statistics. By giving a detailed overview of the structure of a country’s population at a specific point in time, they provide one of the most important parameters for political action. In addition, in modern statistical systems, population censuses are the data basis for a variety of further statistical information, such as intercensal updates of the number of inhabitants. They provide the basis for the statistical fields which either describe the population or in which population data are integrated. Furthermore they allow drawing reliable population samples and performing qualified extrapolation of sample results. This article focuses on the relevance of censuses in general and, more specifically, of the current 2011 Census in Germany. Following a historical overview in the first part of the article, the second part describes the various definitions of “population”, the relevance and issues of defining the survey unit and of operationalising concepts of variables. In the third part, some examples illustrate various areas that are relevant for statistics and social policy and for which the 2011 Census will provide information, while the fourth part provides an outlook on how the census can be developed further, both in terms of methodology and contents.