The period of Ramadan is determined by the phases of the moon and its sighting by local religious authorities, meaning the exact day of celebration varies by locality.
Palestinians in Jerusalem, the West Bank and Gaza Strip have attended Eid al-Fitr prayers marking the end of the fasting month of Ramadan.
Thousands of Muslim worshippers flocked to the al-Aqsa mosque in Jerusalem's Old City, Islam's third-holiest site, before heading to graveyards at the ancient Muslim cemetery to pray for their loved ones - a tradition on the morning of Eid.
While Eid is meant to be a joyous occasion at the end of Islam's holy month of Ramadan, in many parts of the world ongoing conflict has marred celebrations.
With a conflict waging in Yemen for nearly two years, many residents of the capital, Sanaa, say they had little to look forward to during Eid.
"I swear by God, this is the worst year. It's not like the previous year because there are no pensions or salaries. People can't even buy Eid clothes."
For the first time in several years, residents in the Iraqi city of Mosul celebrated their Eid holiday without the presence of IS after the militants were dispersed from much of the city.
Maher Bakr celebrated Eid with a group of other young children on the streets of Mosul.
"Thank God, we were living before in hell. You know what Daesh did. We had no food and no water. The situation was very difficult. We were living in fear with no food and water. Thank God it is better now."
Syrian President Bashar al-Assad made a rare trip outside the capital, Damascus, to Hama to deliver prayers.
While in Damascus, in the historical Al-Hamidiyh market, crowds of people visited the souk to buy new clothes for the celebrations.
Ahmad Abu Dahab says despite ongoing conflict in Syria he's trying to make the best of Eid for the sake of his children.
"We have to do our best for them. We are in an exceptional situation, the situation is hard economically and socially and we are trying our best to satisfy their needs but not a hundred per cent."
There was a brief Eid ceasefire in the Philippines in the southern city of Marawi, where the government is trying to contain IS militants.
In Nigeria, currently waging a battle against Islamic fundamentalists, those attending prayers in the capital Lagos called for more to be done to wipe out extremism in the country.
And in Russia, where 15 per cent of the population is Muslim, worshippers from central Asian countries packed Moscow's largest mosque.
In London, Muslim residents from five London tower blocks marked Eid at a community centre in Camden instead of at home, after concerns over the safety of their apartment blocks following the deadly Grenfell Tower blaze.
London imam Imran Khan says Ramadan gave people the strength to help endure difficult times.
"As a community we have seen all of us together and it is a beautiful scene and I know a lot of us are going through difficult hard times, but and the one thing we learnt from the month Ramadan is that the month Ramadan is about patience, and when we go through difficult times, patience is the way that we move forward."
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