Lukashenko faces three challengers, two of them representing the ex-Soviet state's small liberal and nationalist opposition.
A candidate scoring 50% plus one vote from ballots cast is declared elected for a five-year term. Preliminary results are expected in the early hours on Monday.
Here are short biographies of the candidates.
Alexander Lukashenko, 51, incumbent president. In power since 1994, he is criticised by the opposition and the West for closing independent media, cracking down on opponents and rigging elections since the mid-1990s.
Lukashenko is popular, especially among elderly and rural voters. A teacher by training and a former state farm boss in Soviet times, he is dubbed 'batka' (father) for his iron fist but also for his down-to-earth style.
A supporter of a "union state" with Russia, Lukashenko refuses to introduce market reforms and backs strong state intervention in the economy.
An avid ice hockey player and head of Belarus's Olympic committee, Lukashenko is a non-smoker who drinks occasionally. He likes skiing, tennis and promotes a healthy lifestyle.
Alexander Milinkevich, 58, independent, backed by most opposition parties and groups as their best hope to challenge Lukashenko.
The president's key challenger is
Alexander Milinkevich, a lecturer
Milinkevich, a lecturer, was little known to voters before his nomination in October 2005. He headed an independent think-tank to promote regional development and was a deputy mayor in western Belarus.
Alexander Kozulin, 50, leader of the opposition Social- Democratic party.
The former rector of the Belarussian State University is popular among fellow academics, but his strong criticism of the president has often angered the authorities. Lukashenko brands him "the candidate of crime".
Kozulin, like Milinkevich, rarely appears in state media. He has drawn attention to his candidacy by other means - he attempted to gain entry to a gathering backing the president, prompting police to beat and briefly detain him.
He faces charges after smashing a portrait of Lukashenko at a police station.
Sergei Gaidukevich, 51, a parliamentary deputy loyal to Lukashenko. The former military officer ran in the previous presidential election in 2001 and finished last out of three candidates.