This book constitutes the thoroughly refereed post-conference proceedings of the Third Annual Privacy Forum, APF 2015, held in Luxembourg, Luxembourg, in October 2015. The 11 revised full papers presented in this volume were carefully reviewed and selected from 24 submissions. The topics focus on privacy by design (PbD), i.e. the attempt to combine technical and organizational measures to ensure the basic rights of the individual. The papers are organized in three sessions: measuring privacy; rules and principles; legal and economic perspectives on privacy.