ENThe overarching aims of the present book are to provide ready-to-use data on the phenomenon of singlehood in Europe and deeper insight into the factors associated with the happiness of single adults in Europe. Although the issue of happiness as a function of relationship status was previously analyzed by Kislev (2020a) based on the data collected in the ESS, he did not focus solely on single people but rather compared single with coupled individuals. Furthermore, Kislev (2020a) selected only individuals aged 30 and above and utilized data collected from only the first to the eighth ESS rounds (2002–2016). Our book overcomes these limitations by utilizing the data collected in nine ESS rounds (2002–2018) and by concentrating on single individuals aged at least 18 years because of the contemporary stronger detachment from traditional developmental tasks in the domain of marriage and family from a specific age (e. g., Bühler & Nikitin, 2020). We hope that the current book contributes to further making a shelter for single individuals in science and to the recognition of singlehood as a valid and authentic way of life and area of scientific research.