EID al-Adha marks the end of Hajj, the annual Islamic pilgrimage to Mecca in Saudi Arabia.
It is one of the two Eid celebrations - Eid al-Adha and Eid al-Fitr - and is often considered the holier of the two. Here's everything you need to know about the religious festival...
Millions of Muslims around the world will gather to mark one of the holiest days in the religious calendar.
Large groups get together to pray while enjoying feasts and wearing their best clothing.
In 2018 it will begin in the evening of August 21 and end four days later on August 25.
Traditionally, the festival lasts for four days but public holidays vary around the world - with Arab countries observing a nine-day public holiday.
What is the Islamic festival about?
It is also known as the Feast of the Sacrifice or the Greater Eid.
The celebration revolves around when Allah appeared to Ibrahim in a dream and asked him to sacrifice his son, Ishmael, as a sign of his faith.
It’s similar to the Christian and Jewish stories in which God asked Abraham to sacrifice his son Isaac, but spared him from doing so.
It is a celebratory festival and men and women will dress up for the occasion.
How is it celebrated?
Friends and family gather together to exchange gifts and money and eat traditional food.
It is tradition to give gifts and be given new clothes during Eid al-Adha.
Sacrifice is a huge part of the tradition.
In some countries, families buy, keep and slaughter their own animals.
Islamic rules state the animal must be in good health and an adult.
The meat from the sacrificed animal is traditionally divided into three parts.
A third is kept by the family, a third is given to friends and relatives, and a third is donated to the poor.