"Sunday School" is the generic name for many different types of religious education pursued on Sundays (traditionally, though not exclusively, in the morning) by various Christian denominations, especially in the United States. Most Protestant churches operate Sunday Schools. Sunday Schools, contrary to the name, are virtually never recognized educational institutions; rather than offering formal grades or transcripts, Sunday Schools simply attempt to offer meaningful instruction concerning Christian doctrine and keep little or no record of performance for any given week. Attendance is often tracked as a means of encouraging children to appear regularly (awards are frequently given for reaching attendance milestones).

Sunday School often takes the form of a one hour Bible study which can occur before, during, or after a church service. While many Sunday Schools are focused on providing instruction for children (especially those occurring during service times), adult Sunday School classes are also popular and widespread.

Sunday School teachers are usually laymen who are selected for their job by a church board, normally because of their advanced experience with the Bible—few teachers receive any formal training in education, though many Sunday School teachers have a background in education as a result of their occupations.