The Sicilian Defense (1.e4 c5) contains countless variations and sub-variations that have been discussed in detail at all levels of play for many years. Even "small" specialized systems have been covered in exhaustive detail in book after book. That is why this book is unique, The Carlsen Variation, which arises after 1.e4 c5 2.Nc3 d6 3.d4 cxd4 4.Qxd4, has never previously been covered in detail before. The variation was uncorked by World Champion Magnus Carlsen in 2018 and has since been played by several other top grandmasters such as Fabiano Caruana, Hikaru Nakamura, and several others. Yet despite this attention, the theory of the variation is largely unexplored and this book aims to set this discrepancy straight. Main lines are established and carefully analyzed with hundreds of new ideas and improvements suggested along the way. For the reader, this book is an excellent resource to get the opponent out of their opponent's "book" into our book. Time to have some fun in the Sicilian - enjoy!