Vessels sailing under the Sao Tome and Principe Country Flag are required to have on board this flag as part of flag state requirements that derive from maritime regulations in the International Code of Signals and the International Safety Management (ISM) Code. These codes are published by the International Maritime Organization (IMO) as an ongoing effort to reinforce maritime safety procedures and communications to the international maritime community. Fleet management companies and ship owners are responsible to ensure that each vessel in their respective fleets have the appropriate flag signage onboard to be in compliance. This flag is used to identify the flag state a vessel is sailing under and to communicate with other vessels under the provisions of the International Code of Signals.
The Sao Tome and Principe Country Flag is represented by three horizontal bars. A green bar at the top and an equally sized one on the bottom are bisected by a yellow bar that is twice as thick. A red isosceles triangle graces the left side, or hoist side of the flag, pointing toward the fly edge. Two black five pointed stars appear in the center of the yellow bar, offset toward the right side of the flag. The two stars represent the two main islands that define Sao Tome and Principe. The green bars represent the abundant vegetation on the islands, while the yellow stands for the cocoa that is so important to the country's economy and lifestyle. Red represents the struggle for independence.