This book explores the work of the European Ombudsman and her or his contribution to holding the EU institutions, bodies, offices and agencies to account, through examination of complaints on maladministration, own-initiative inquiries and other proactive efforts. It considers the Ombudsman's current institutional and constitutional position and her or his 'method' of dealing with complaints, and unravels the depth of subject matters that fall under the Ombudsman's remit. A separate chapter focuses on transparency and access to documents. The last part of the book critically reflects upon the present mandate and practice of the Ombudsman, and discusses a number of possible proposals for improvement. This work has interdisciplinary appeal and will engage scholars in law, political science and public administration, as well as EU and national policy-makers.