The IMO Compendium is a book that contains all problems ever shortlisted for the International Mathematical Olympiad (IMO) with solutions, and all of the available longlisted problems. To the best of our knowledge, such a huge collection of IMO related problems has never been assembled before. The book has been published by Springer in the series Problem Books in Mathematics.

We are very proud and excited to be presenting to you this book. We suspect that it will be of significant benefit for any high school student wishing to prepare for math competitions or simply raise his or her skill level in mathematics. The book is especially suitable for anyone training to qualify for or participate on the IMO. The book offers a great number of problems of all levels of difficulty with detailed solutions and as such is suitable for all high school students wishing more than pure school mathematics. In an attempt to present as many common ideas as possible, it offers more than one solution to many problems. It also contains a lot of problems without solutions for practice (but all shortlisted problems are solved). A high school student on any level of knowledge could spend an enjoyable year or so going through the numerous problems and novel ideas presented in the solutions and emerge ready to tackle even the most difficult problems. This book will also be of interest to high school coaches and others interested in mathematical problem solving.

Special thanks are due to Prof. Vladimir Mićić, for some of the oldest manuscripts, and to Prof. Zoran Kadelburg. We also thank Prof. Djordje Dugošija and Prof. Pavle Mladenović. In collecting shortlisted and longlisted problems we were also assisted by Prof. Ioan Tomescu and Hà Duy Hưng.

Special thanks for helping us in finding the errors go to our copy-editor David Kramer, Prof. Titu Andreescu (and his group), and to Prof. Ljubomir Čukić. We also thank Prof. Abderrahim Ouardini for sending us the list of countries of origin for the shortlisted problems of 1998, and Prof. Dorin Andrica for helping us compile the list of books for reference.

The illustrations of geometry problems were done in WinGCLC, a program created by Prof. Predrag Janičić.

More detailed acknowledgments can be found in the sample chapter of the book.