The IMO (International Maritime Organization) is the United Nations specialized agency that sets the rules for international shipping. This article explains the role and structure of the IMO and how its conventions come into effect.

Role of the IMO

The IMO is responsible for the safety and security of shipping and for preventing marine and atmospheric pollution by ships. It is the body that sets global standards for the safety, security, and environmental performance of international shipping.

International shipping carries more than 80 percent of global trade. If standards differed from country to country, some operators might cut costs by compromising on safety or environmental measures. The IMO therefore aims to create a regulatory framework that is fair and effective, and that can be universally adopted and implemented.

Its areas of work are wide-ranging. In addition to ship design, construction, equipment, manning, operation, and disposal, they include protection of the marine environment, energy efficiency, maritime education and training, and maritime traffic management.

History

The convention establishing the IMO was adopted at an international conference in Geneva in 1948 and entered into force in 1958. The Organization held its first meeting the following year, in 1959.

It was originally called the Inter-Governmental Maritime Consultative Organization (IMCO) and was renamed the IMO in 1982. Its headquarters are in London.

Japan has been a Member State since the Organization was founded and has taken part in its work as a Council member ever since. In 2025, Japan’s contribution was the tenth largest among Member States.

Membership and Structure

As of January 2026, the IMO has 176 Member States and 3 Associate Members, including Hong Kong.

The main organs of the IMO are as follows.

Table 1 Main Organs of the IMO

Organ	Composition	Main Role
Assembly	All Member States; normally meets once every two years	Highest governing body. Approves the work programme and budget, and elects the Council
Council	40 States elected by the Assembly for two-year terms	Executive organ. Supervises the work of the Organization under the Assembly, and performs the functions of the Assembly between its sessions
Committees	Five committees, and seven sub-committees that assist the Maritime Safety Committee and the Marine Environment Protection Committee	Consider conventions and standards in each field

The Secretariat consists of the Secretary-General and some 300 international staff at the headquarters in London.

Amendments have been adopted to increase the number of Council members to 52.

The five committees are as follows.

• Maritime Safety Committee (MSC)
• Marine Environment Protection Committee (MEPC)
• Legal Committee
• Technical Cooperation Committee
• Facilitation Committee

How Conventions Come into Effect

The adoption of a convention at the IMO does not by itself bind any country. A convention binds a country only after its government expresses consent through ratification, acceptance, approval, accession, or a similar procedure.

Amendments to conventions use the “tacit acceptance” procedure. Under this procedure, an amendment enters into force on a set date unless a certain number of Contracting Parties object within a specified period. For example, an amendment to the annex of the SOLAS Convention enters into force unless it is objected to by more than one third of Contracting Governments, or by Contracting Governments owning 50 percent of the world’s gross merchant tonnage.

As a result of this procedure, amendments now generally enter into force within 18 to 24 months.

The Role of States in Implementing Conventions

The IMO itself has no power to enforce conventions. It is individual countries that actually apply them.

• Flag States: Apply conventions to their own ships and crews. Flag States are primarily responsible for imposing penalties for violations on the high seas.
• Port States: Can inspect foreign ships in their ports. If a violation is found, they can either prosecute under their own law or report it to the flag State. Under the SOLAS Convention, a ship can be prevented from sailing if there are clear grounds for believing that the condition of the ship and its equipment does not substantially correspond with the particulars of its certificates.

However, for the convention on seafarer training and certification, there is a mechanism under which Contracting Parties submit relevant information to the Maritime Safety Committee.

Major Conventions

The IMO’s main conventions fall broadly into three fields: maritime safety, prevention of marine pollution, and liability and compensation. Representative conventions are as follows.

Table 2 Representative IMO Conventions

Abbreviation	Full Name	Year Adopted
SOLAS	International Convention for the Safety of Life at Sea	1974
MARPOL	International Convention for the Prevention of Pollution from Ships	1973
COLREG	Convention on the International Regulations for Preventing Collisions at Sea	1972
STCW	International Convention on Standards of Training, Certification and Watchkeeping for Seafarers	1978

About This Article

Sources

• International Maritime Organization, “Introduction to IMO”
• International Maritime Organization, “Structure of IMO”
• International Maritime Organization, “Brief History of IMO”
• International Maritime Organization, “Conventions”
• Ministry of Land, Infrastructure, Transport and Tourism, “Overview of the IMO (International Maritime Organization)” (in Japanese)
• Ministry of Foreign Affairs of Japan, “Overview of the International Maritime Organization (IMO)” (in Japanese)

(Last accessed: October 15, 2026)


*This article was compiled based on the author’s understanding and practical knowledge, with reference to the above literature.