The Holy Ramadan, the lunar month of self-purification through fasting and abstinence, begins in the country on Saturday.
The National Moon Sighting Committee took the decision in a meeting as the new crescent moon was sighted in Bangladesh sky on Friday.
Ramadan, also known as Ramzan, is the ninth month in the Islamic calendar.
It is a time when Muslims around the world focus on prayers, fasting, giving to charity and religious devotion.
They will start saying their Taraweeh prayers on Friday night and have their Sehri early Saturday.