The traditional idea that marriage between men and women is the centre of social life has increasingly lost plausibility and acceptance in recent decades. In the course of the amendment to the Civil Code, gender differentiation has been replaced by the definition of marriage as a community of assistance and responsibility. This stipulation forms the provisional endpoint of corresponding provisions of the past few decades also on social approaches to homosexuality. But how does Christian theology relate to these changes? From which biblical, historical, and systematic resources do marriage and, in their environment, partnership and sexuality become topics of theology? These questions are addressed in the articles of this volume, which go back to a lecture series at the Faculty of Theology in Leipzig in the summer semester of 2019.