North American English regional phonology is the study of variations in the pronunciation of spoken North American English (English of the United States and Canada)—what are commonly known simply as "regional accents". Though studies of regional dialects can be based on multiple characteristics, often including characteristics that are phonemic (sound-based, focusing on major word-differentiating patterns and structures in speech), phonetic (sound-based, focusing on any more exact and specific details of speech), lexical (vocabulary-based), and syntactic (grammar-based), this article focuses only on the former two items. North American English includes American English, which has several highly developed and distinct regional varieties, along with the closely related Canadian English, which is more homogeneous geographically. American English (especially Western dialects) and Canadian English have more in common with each other than with varieties of English outside North America.
The most recent work documenting and studying the phonology of North American English dialects as a whole is the 2006 Atlas of North American English (ANAE) by William Labov, Sharon Ash, and Charles Boberg, on which much of the description below is based, following on a tradition of sociolinguistics dating to the 1960s; earlier large-scale American dialectology focused more on lexicology than on phonology.