The electoral process will take place over three days from 9 a.m. (0700 GMT) until 9 p.m. (1900 GMT) local time, with results due to be announced on Dec. 18, Anadolu Agency reported.
While al-Sisi is poised to win a third term, his opponents are Farid Zahran, head of the Egyptian Social Democratic Party, Abdel-Sanad Yamama, leader of the Egyptian Wafd party, and Hazem Omar, head of the Republican People's Party.
In Egypt's 27 governorates, voting began in 11,631 polling stations in 9,376 main electoral centers, according to national news agency MENA. About 67 million voters are entitled to vote.
The National Elections Authority said it approved 24 embassies, 67 diplomats, and 220 international observers from 14 foreign organizations, along with 68 local organizations and 22,340 personnel from six local NGOs to observe the elections.
The voting process for Egyptians abroad took place from Dec. 1-3 at 137 headquarters of Egyptian diplomatic missions in 121 countries.
President al-Sisi won his first and second terms in 2014, and 2018, while constitutional amendments later extended the presidential mandate from four to six years and allowed him to run for a third term.