The Professional Association of Diving Instructors (PADI) is the world's largest recreational diving membership and diver training organization.

ADI members, including dive centers, resorts, educational facilities, instructors, and divemasters, teach the majority of the world's recreational divers.

PADI operates offices in Australia, Canada, Switzerland, Japan, Sweden, the United Kingdom, 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.

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 using books, computer based training using CD-ROM or online learning. All study options are suplemented with video to help the student diver visualize what they have read.

Confirmation of the student diver'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.

PADI courses are performance based dive programs, and at the introductory level emphasize practical knowledge, safety and motor skills. The foundations of Diving physics, physiology and chemistry are built during entry level programs. The more esoteric details of these concepts are left for later courses when the diver has gained practical knowledge and experience beyond the entry level. These practices fall within current modern learning philosophies[citation needed] and receive regular updates via peer review. In addition to this, other dive instruction programs have adopted similar techniques.