The national flag of Bangladesh (বাংলাদেশের জাতীয় পতাকা) was adopted officially on 17 January 1972. It is based on a similar flag used during the Bangladesh Liberation War of 1971. The Flag was designed by Quamrul Hassan.
A red disc is on top of the green field, offset slightly toward the hoist so that it appears centred when the flag is flying. The red disc represents the sun rising over Bengal, and also the blood of those who died for the independence of Bangladesh. The green field stands for the lushness of the land of Bangladesh.
Source: Flag of Bangladesh