Assistant Language Teacher, often abbreviated to ALT, is a term used primarily by the JET Programme to identify native speakers of a language employed to assist in teaching that language in elementary, junior high and high schools in Japan. When English was the only foreign language taught by JET participants, teachers were called Assistant English Teachers, or AETs.

ALTs can be assigned to a single "base" school, and teach virtually all of their classes there, or be assigned to an office or base school, and visit several schools on a rotating basis. ALTs at senior high schools (grades 10-12) tend to have a base school, while those teaching junior high (grades 7-9) and elementary (grades 1-6) tend to visit several schools.

ALTs receive relatively high salaries and have fewer responsibilities than their Japanese colleaguges. However, ALTs do not receive the semiannual "bonuses" that Japanese teachers do. Many ALTs complain of being underutilized, but most have fewer qualifications and less experience than professional teachers. On the other hand, few Japanese teachers of English have any training in team teaching, and receive little or no guidance in how to maximize the presence of an ALT.

Some Japanese, particularly teachers, complain that ALTs are overpaid. However, many forget that ALTs are willing to leave their home countries for an extended period, and while they are expected to learn Japanese, many have no Japanese language ability before arrival. The high salary is one way to compensate for the many challenges of living in a truly foreign country whose language they do not understand.