A correspondence course is a form of education known as distance learning. The typical correspondence course involves the exchange of teaching materials between a student and teacher geographically remote from each other. The student obtains a textbook locally, and lesson plans, lecture notes and problem sets are sent by the instructor to the student. The student sends completed assignments back to the instructor for grading, and exams are administered by a proctor local to the student.

Traditionally, a correspondence course could work no faster than the mail system. With improvements in technology, communication has become virtually instantaneous. Lecture notes and problem sets can be distributed by email or posted on a web site. Even textbooks can be distributed in electronic form as PDF files.

A correspondence course is not limited to any specific level of education. While high school completion programs, such as the GED, may be the most familiar form of distance learning, the earliest use was actually at the university level. This began in the United Kingdom, which needed a way to educate its own people despite having an empire spanning the entire globe. To this day, very prestigious programs such as that of the London School of Economics are available to anybody, anywhere, at reasonable cost as a correspondence course. These courses are taught and graded to the same high standard as the resident versions.

Some educators have suggested that more and more individuals will learn through a correspondence course in the future. As technology makes remote communication increasingly personal through instant messaging, voice and video chats, the need to be in the same room as an instructor decreases. Futurists have envisioned a time when the classroom becomes virtualized into cyberspace, allowing top-flight instructors to reach many more students than they otherwise could.

A high school correspondence course will generally be administered at the state or provincial level, whereas a university level correspondence course will be administered by the university itself or a union of universities. The largest such institution in the world is The Open University in the United Kingdom. The Open University offers correspondence courses leading to degrees from such prestigious institutions as the University of London and Imperial College. More recently, Universitas 21 Global, a partnership between a number of leading international universities and Thompson Learning, was created to provide a global MBA program.

Students interested in a correspondence course must take care to verify the accreditation of the program. Particularly in the United States, so-called diploma mills are notorious for offering low-quality courses leading to unrecognized degrees.