Lions Clubs International is the world's largest service club organisation with 45,000 clubs and nearly 1.3 million members in 197 countries around the world. The international headquarters is situated in Oak Brook, Illinois.

It was founded in the U.S.A. in 1917 by Melvin Jones and became truly International on March 12, 1920 when the first club was established in Canada--in Windsor, Ontario. Membership is by invitation and attendance at meetings is expected on a monthly or fortnightly basis. Politics, religion or other contentious subjects are generally forbidden at club meetings. Lions are truly a community-based organisation with a hierarchy that can take a member from a club to office at zone, district, national and international levels. An interesting aspect of the operation of Lions Clubs is that all funds raised from the general public are used for charitable purposes, with the administration costs of a Club kept strictly separate and paid for by its members.

The average age of Lion members is increasing and the average membership of clubs is decreasing in the Western world. This is typical of other service clubs such as Rotary International.