For weeks, thousands of people have been dressing up and gathering at campaign rallies, but the country's new government won't be known until August, reports the Australian Broadcasting Corporation.
This is what you need to know about PNG's election.
A total of 3625 people have nominated to compete for the 118 seats in parliament.
PNG currently has 111 MPs, but seven new districts were created just weeks before the start of the election period.
Only 167 candidates are women — less than 5%.
PNG is currently one of only four countries in the world that has no female MPs, after an all-male parliament was elected in 2017.
Three candidates are facing exclusion from the election because of criminal convictions, following a Supreme Court ruling on eligibility this year.
One candidate was convicted of murder, another of rape and a third of conspiracy to defraud.
They are not the only candidates facing legal issues.
A sitting MP, Lohia Boe Samuel, has been charged with murder after a shooting in a Port Moresby restaurant in March.
That court case is still under way, so he is eligible to recontest his seat, which he is.
Meanwhile, another candidate in the highlands has been arrested and charged with murder during the campaign.
It came after shots were fired after a fight broke out following game two of State of Origin.
PNG does not have a two major party system like Australia.
Maholopa Laveil, a lecturer from the University of Papua New Guinea, said more than 50 parties were contesting this election.
"About half of those get voted in," he said.
"So, there were about 21 parties in 2017 that were elected in. That number grew to about 25 over the course of parliament as MPs switched and formed new parties in parliament."
Most are small, only having one or two MPs, but bigger parties with 6-9 MPs can "wield a lot of power" as coalitions are essential to forming — and staying — in government, he said.
Elections are held every five years in PNG and campaigning has run for the past six weeks.
During that time, huge political rallies have been held across the country, with candidates taking helicopters, boats, buses and planes to reach all the remote corners of PNG and speak to voters.
Three weeks have been set aside for voting from today, with different areas to vote on different days, and one week for counting.
But Electoral Commissioner Simon Sinai has now said he wants to try to complete voting in two weeks because such a limited time frame has been set before the results legally have to be handed up, on July 29th.
The final voting schedule was not released until Friday — just 72 hours ahead of polling starting, and voting in the capital city, Port Moresby, has been pushed back from today until Wednesday.
The delays and apparent disorganisation have caused some alarm.
"We are trying our best to do as much as we can, with our available resources and time," Sinai said.
More than 6000 teams will be sent out to conduct polling during the election.
PNG maintains a vibrant democracy, but its elections are considered one of the most challenging in the world to conduct because of remoteness and difficult terrain, along with the cultural diversity and poor infrastructure.
As counting is completed, MPs will go into what are known as camps, where they go into hotels to form coalitions.
The party with the highest number of MPs will be called on to form government but it will not have a majority in its own right, so support from smaller parties is vital.
The final makeup of the government will be revealed in the first parliament sitting in August.
Parochial issues generally dominate elections in PNG.
Laveil said PNG was termed "clientelistic", meaning, "people tend to vote on what you give them in elections".
Voters will often be swayed by a candidate who has brought something tangible to their area or offered inducements.
People may also be influenced by relatives or the views of community members.
With 1000 tribes and 800 language groups, political culture varies across the country, and there are also differences between rural and city voters.
"The urban seats, there are more educated voters, and national and international issues tend to influence voters, but in the rural seats, it's local issues," Laveil said.
PNG's last election in 2017 was marred by violence and allegations of widespread fraud and vote-buying in some areas and was considered by many observers as the worst election on record, and it is feared there will be similar issues this election.
Most campaign events have been peaceful, but there have been some outbreaks of violence in the lead-up to the election.
It is estimated 30 people have died so far - some in violent clashes, others in road accidents travelling to and from events.
A minister's convoy was torched in one area and an electoral official was shot in another.
There are concerns that the common roll has not been properly updated and that some people will miss out on the chance to vote and that could lead to violence during polling.
"At least one million, that's the estimate at the moment, will not be able to cast their vote," Dr Henry Ivarature, a past election observer from the Australian National University, said.
"The two governments [that have been in power since 2017] did not provide the electoral commission the financial resources to conduct a full and complete update of the electoral roll."
Sinai has defended the updated roll but also conceded he had wanted to compile a new one but did not have the funding for it.
There have also been some issues and concerns with the transport of ballot papers and the appointment of electoral officials.
Despite the problems and delays, Sinai told the ABC you could not "draw the conclusion" that the election could fail.
"The people are ready, the materials are on the ground in the provinces," he said.
But he did not rule out that some electorates could fail.
"For now, I don't think there's anything failed."
Around 7000 PNG security personnel will be working during the election and police have set up a toll-free number for people to report electoral offences.
The million-kina question!
The two most likely candidates are current Prime Minister James Marape and the man he deposed, former prime minister Peter O'Neill.
Marape's Pangu Party is contesting more than 80 seats, while O'Neill's People's National Congress is contesting more than 90.
Other major parties expected to have a substantial number of MPs are the National Alliance Party, PeopleFirst, United Resources Party and PNG Party for Change.
Their party leaders will also be hoping to take the prime minister's spot.
PNG is known a
"The time between [when] the results are announced to the first parliament sitting, is when horsetrading begins to happen," Laveil said.
In that time, MPs may switch parties, coalitions will rise and fall and independents will form allegiances with different parties.
Incumbents, like Marape's party, are usually re-elected in PNG, partly because they have control of government finances, which is a big advantage when campaigning.
But O'Neill's party has put together a very well-funded and well-organised campaign to challenge Marape's the land of the unexpected and that goes double when it comes to politics.
The election is being closely watched given the geostrategic competition in the Pacific and the increasing battle for influence between China and Western allies like Australia and the US.
While it is colouring how outsiders watch the election, geopolitics is not a major issue for voters.
PNG has long held a "friends to all and enemies to none" foreign policy, which it will be keen to maintain despite the growing tension.
The frontrunners for prime minister have said they do not envisage making big changes to foreign relations or security ties.
Australia is PNG's biggest security partner, with members of the Australian Federal Police and the ADF based in the country full-time, and it is a position Australia wants to maintain.
Additional ADF members and aircraft are in PNG assisting with the election and the ballot papers have been printed in Australia.
But China is a large trading partner and the biggest destination for PNG's exports.
In recent years, its presence in construction and development assistance in the country has also grown, and some Chinese-backed project ideas have raised alarm in Canberra.
China's ambassador has made an appearance on the campaign trail, popping up at the official opening of a hospital in Enga, which was largely funded with an Exim Bank loan.
Australia's Prime Minister Anthony Albanese and other ministers are expected to visit PNG quickly after the new government is formed.
It is expected several other countries will also be interested in high-level meetings.