There are no official data, but it is estimated that four million adults in Germany have little or no reading, writing and numeracy skills, so that they are known as "functionally illiterate". This is a fact which was long ignored. In this contribution, literacy activities and research in Germany are analysed through a human rights-based approach. I argue that illiteracy in a knowledge-based society like Germany has to be understood in terms of a lack of social inclusion and participation. In Germany, the aims of the United Nations Literacy Decade (2003-2012) have not yet been achieved. (Contains 1 table and 2 figures.)