Voters will also cast a ballot in a referendum on proposed amendments to the Constitution, including changes to the Bill of Rights.
Zambia holds a general election on Thursday, pitting President Edgar Lungu as the flag-bearer for the ruling party against opponents who blame him for a weak economy, led by front-runner Hakainde Hichilema.
Below are some of the key facts about the election and referendum in Africa's second-biggest producer of copper, which is a mainstay of its economy.
- There are 6.6 million registered voters in a country with a population of about 15 million.
- Voting starts at 6 am local time (0400 GMT) and ends at 6 pm (1600 GMT).
- Zambians will be voting for the posts of president and a running mate who will be the vice-president, 150 members of parliament, mayors and councillors.
- Voters will also cast a ballot in a referendum on proposed amendments to the Constitution, including changes to the Bill of Rights.
- Lungu, who heads the Patriotic Front party, is a former lawyer. He narrowly beat Hichilema, known locally as "HH", of the United Party for National Development in a vote last year to replace Michael Sata, who died in office in October 2014.
- Forum for Democracy and Development leader Edith Nwakakwi is expected to run a distant third.
- To win, a presidential candidate must garner 50 percent of the valid votes cast plus at least one additional vote.
- If none of the candidates receive the required amount of votes, a re-run for the top-two candidates will be held within 37 days.
- For MPs, mayors and councillors, the candidate with the largest number of votes will be declared to have won.
- The final results will likely be known by Saturday, according to electoral officials.