\title{The Dade group of a fusion system} \author{Markus Linckelmann} \address{Markus Linckelmann, University of Aberdeen, Aberdeen, UK} \author{Nadia Mazza} \address{Nadia Mazza, University of Aberdeen, Aberdeen, UK} \begin{abstract} We define a notion of a Dade group of a fusion system and show that some of the gluing and detection results for Dade groups of finite $p$-groups due to Bouc and Th\'evenaz in \cite{BoTh2}, \cite{BoTh3} extend to Dade groups of fusion systems. \end{abstract} Status: to appear in the Journal of Group Theory