The landmark referendum is a key part of the 2005 Comprehensive Peace Agreement (CPA) that ended decades of war between the Arab-dominated northern government and the rebel forces from the Christian and animist southern region.
Below is a timeline of key events leading up to the vote.
The Sudanese government and southern rebels (the Sudanese People’s Liberation Movement) agree to include a power-sharing plan in a peace deal to end two-decade conflict.
The Sudanese government and southern rebels sign the Comprehensive Peace Agreement (CPA), which includes a permanent cease-fire, plans for wealth and power sharing, and an autonomous government in the south.
A Constitution is signed, giving southern Sudan a significant amount of autonomy. Former southern rebel leader John Garang is named first vice president of Sudan. He is killed the following month in a plane crash.
A power-sharing government is formed in Khartoum, Sudan's capital.
South Sudan forms an autonomous government.
South Sudan temporarily leaves unity government, citing a failure to follow the 2005 peace deal.
Arab militia and southern Sudanese forces clash in Abyei region, which lies between north and south.
Counting begins in national census, one of the requirements for democratic elections and the referendum agreed to in the peace deal.
More fighting breaks out in border region, this time in town of Abyei. Abyei is rich with oil, a point of contention in the upcoming referendum.
South Sudan’s leader and vice president of unity government warns he is preparing forces for the possibility of another war with the north.
Leaders of north and south reach a deal on the terms of the referendum on southern independence, planned for 2011.
Bashir says he will accept results of a referendum, even if it leads to southern independence.
Sudanese President Omar al-Bashir wins Sudan’s first contested presidential election since 1986.
The timetable for the referendum is set. The vote is scheduled for Jan. 9, 2011.
Voter registration for the referendum begins.
Jan. 9, 2011
The referendum vote on South Sudan’s independence will take place.