Self-discipline and reflection
Muslims believe Ramadan to be the month in which the first verses of the Quran, Islam's holy book, were revealed to the Prophet Muhammad more than 1,400 years ago.
Ramadan begins with the first sighting of the the new crescent moon in the ninth month of the lunar calendar, during which Muslims practise sawm, or fasting, from before sunrise to after sunset for the entire month.
Families and friends get up early for suhoor, the last meal eaten before the sun rises, and at the end of a day of fasting, gather for iftar, the breaking of the fast at sunset.
Self-discipline and reflection are primary objectives of the fast in which all physical contact between husband and wife is also abandoned in daylight hours for the duration.
Fasting is also an opportunity to practice self-control and to cleanse the body, which Muslims see as helping their spiritual devotion.
Muslims around the world also consider the month is one of blessing, marked by prayer and charity.
In many Muslim countries, offices are required by law to reduce working hours and most restaurants are closed during daylight hours.
Barak Obama, the US president, released a video message to the world's Muslims in a bid to re-cast the United States' engagement with a number of Islamic countries.
"All of these efforts are part of America's commitment to engage Muslims and Muslim-majority nations on the basis of mutual interest and mutual respect," Obama said.
"And at this time of renewal, I want to reiterate my commitment to a new beginning between America and Muslims around the world."