Pro-democracy protest groups hope the vote will send a message to the Chinese government after five months of unrest and anti-government protests.
Long queues formed on Sunday amid fears polls might be closed by authorities if violence disrupted the election.
In the run-up to the election, pro-democracy protest groups had urged people not to cause disruption. No trouble has been reported so far.
A record 4.1 million people have registered to vote – more than half the population of 7.4 million.
More than 400 councillors are due to be elected to Hong Kong’s district council.Polls opened at 07:30 local time (23:30 GMT) on Sunday.
By 13:30 more than 1.5 million people had voted (36.89% of all registered voters) compared to 551,183 (17.66%) within the same timescale in the last such elections in 2015.
In total, 1.467 million people voted in the last poll. Only 3.1 million people were registered to vote in that election.
More than 1,000 candidates are running for 452 district council seats which, for the first time, are all being contested. A further 27 seats are allocated to representatives of rural districts.
Currently, pro-Beijing parties hold the majority of these seats.