The Professional Association of Diving Instructors (PADI) is the world's largest recreational diving membership and diver training organization founded in 1966 by John Cronin and Ralph Erikson.

PADI members, including dive centers, resorts, educational facilities, instructors, and divemasters, teach the majority of the world's recreational divers.[citation needed] PADI operates offices in Australia, Canada, Switzerland, Japan, Norway, Sweden, the United Kingdom, New Zealand and the United States. The corporate headquarters, PADI Worldwide, is located in California, United States of America. PADI Offices serve more than 130,000 individual professional members and more than 5,300 dive centers and resorts in more than 180 countries and territories. Translations of PADI materials are available in more than 26 languages. [1].

PADI courses range from entry levels (such as Scuba Diver and Open Water Diver) to master scuba diver and a range of instructor certificates. Via their affiliate Diving Science and Technology (DSAT) they also offer various "Technical" diver courses, including decompression diving, Trimix diving and gas blending.

The PADI system is composed of modules with standardized learning objectives divided into theory and practical skills development. Theory is mainly conveyed by way of self-study (books and video) with confirmation of the student's level of mastery in standardized knowledge review sessions with a scuba instructor. Practical skills mastery is obtained through confined water training (pools or relative shallow water) and performance evaluations in open water. Upon completion of each course, a certification is issued to the student.