The purpose of this book is to provide readers with a thorough introduction to the essential design and operation aspects of olefins plants. For this purpose, it is necessary to develop the knowledge of the readers who are interested to know more about olefins plants employing steam-cracking technology. The author has gathered and developed this book based on extensive experience in many olefins projects as well as olefins operating plants. Included with this book are valuable materials provided by some contributions representing top and reputable olefins licensors and olefins equipment manufacturers for readers to gain insight information and content about steam-cracker plants. The contributors are Linde, Chevron Phillips Chemical Company (CP-Chem), TSKE, Graham, NATCO, SNM, and YJ-TMC. An effort has been made to include essential and useful material for readers in the form of guidelines and suggestions (G&S) as well as design and operation checklists gathered and based on the author's extensive experience in many steam-cracker plants.