While polling suggests George Simion of the far-right Alliance for the Union of Romanians (AUR) party has the best prospects, none of the 11 candidates is expected to win an absolute majority straight away, meaning a run-off is likely.
Polling stations open at 6 am (0400 GMT) and close at 8 pm.
If necessary, a run-off between the two best-placed candidates in the first round would be held on May 18.
In the initial election in November, pro-Russian candidate Călin Georgescu won the first round, having campaigned largely on the online platform TikTok.
However, shortly before the scheduled run-off vote, the Constitutional Court annulled the first round due to irregularities in campaign financing.
Georgescu was also banned from running for president again and has been under investigation by the public prosecutor’s office since February for making false statements about his campaign financing.
It is unclear from advance polling who might emerge in second place after Sunday’s vote. Centre-right National Liberal Party (PNL) candidate Crin Antonescu, conservative-liberal Bucharest Mayor Nicusor Dan and former social-democratic prime minister Victor Ponta are all seen as possible contenders.
Favourite Simion says his aim is to ensure “justice” for Georgescu if he wins the election. He has not ruled out helping Georgescu into the office of prime minister.
In Romania, the president also shapes foreign and security policy.
GNA
PDC