This volume is the first comprehensive English handbook on Japanese dialects. The study of Japanese dialects has a rich tradition, contributing to fields like geolinguistics, sociolinguistics, and phonology. While influenced by Western linguistics, Japanese dialectology has also made significant original contributions through extensive fieldwork and compilation of dialect dictionaries and atlases. Most studies have been published in Japanese, allowing only a handful of foreign specialists to take full advantage of the achievements in Japanese dialectology. This handbook addresses that gap, making dialect data and analyses available to a broader audience and informing specialists about Japanese dialectology's methods and achievements. It focuses on mainland dialects, including the Hachijō language, while a separate handbook covers the Ryukyuan languages, now regarded as sister languages of Japanese.