The elections are crucial in that they will reveal the balance of power between factions in the ruling political establishment and the strength of the incumbent president, Mahmoud Ahmadinejad.
Nearly three years after the pro-reform opposition led huge public protests, the elections should also show how much the general public is willing to support the ruling groups.
One of the most controversial aspects of these elections is the "vetting procedure". The Guardian Council, which supervises the elections, actively vets the candidates so that, in the words of one leading jurist, it "prevents corruption and deviation". Critics see this as a way of ensuring that only loyalists enter the race.
Iran is not a totalitarian state and since the Islamic Revolution in 1979 there has been some openness in which political debate and action has taken shape. Elections are free in the sense that there is some choice of candidates who are elected by universal suffrage.
But critics, including the opposition and the European Union, have expressed doubt that the elections are free and fair.
A number of conservative right-wing factions - so called "Principle-ist" - are competing in the campaign under different coalition lists. No major reformist player is taking part, although a small number of centrist groups and individuals are running, some of them under a pro-reform banner.
1. Government Supporters Front
Right-wing, radical and under President Mahmoud Ahmadinejad's flag
Supporters of President Mahmoud Ahmadinejad are organised in several newly founded groups including the Islamic Government Supporters Front, the Young Advisors of the President, the Justice and Compassion Front and the Unity and Justice Front.
The focus of their rhetoric is social justice and class struggle. They present themselves as the defenders of popular justice and advocates of the poor and claim not to be affiliated to the centres of power or wealth.
However, as the campaign opens, the president's supporters appear to be in a mess. They seem to be relatively disorganised and poorly led, and this is reflected in their tactics. Many of their candidates, including all 24 candidates in Tehran, are reported to have been disqualified in the vetting process.
The group has asked its supporters to register as independent candidates in order to pass the qualification process before re-grouping at a later stage.
It remains to be seen whether government supporters will be able to stage an effective comeback and gain ground.
2. The United Principle-ist Front
Conservative, traditionalist and under the establishment flag
Various conservative forces have come together under the United Principle-ist Front (UPF). They are seen as the old guard and at the moment control the Majlis most of the time. Traditionalist groups make up the main pillar of the UPF, but there are neo-conservative as well as hardliners elements among them.
The UPF is concerned about the possibility of division among conservative ranks and a possible weakening of positions in the face of reformists and foreign powers. They make repeated appeals for unity on the basis of Islam, the constitution and the supreme leader.
The front has distanced itself from government supporters, who are accused of trying to introduce nationalist sentiments, wanting to bypass rules and regulations and seeking relations with the United States.
The UPF also distances itself from the more hardline groups. The front's rhetoric is about loyalty to the supreme leader and the struggle against foreign enemies. But it also speaks of rationalism, realism and good policy.
3. Steadfastness Front (Paydari)
Far right, hardline wing supporting the Supreme Leader Ayatollah Ali Khamenei
The most important radical force competing against Mr Ahmadinejad is the Steadfastness Front (SF). These people are mostly his former supporters who have turned against him and are now re-grouping under the spiritual leadership of Ayatollah Mesbah Yazdi.
The SF presents itself as a friend of Ahmadinejad but stands against his close colleagues. It does not attack him directly because it does not want to undermine the president while he is still in office.
Its programme is very factional and highly charged, with little stress on economic or cultural issues. Their main strategy, factional mobilisation and struggle, aims to maintain the ideological purity of the regime and to eliminate "deviant tendencies".
They say they will not tolerate diversion from radical principles of the revolution and will stand against anyone who might want to revise them. For this reason, their first objective has been to attack the president's group by presenting a "discourse similar to that of Ahmadinezhad but without him".
The SF uses and repeats the president's rhetoric on social justice almost untouched, and even support the government's economic policy, including the removal of state subsidies, the fight against poverty and the reform of the financial sector.
But at the same time they attack his lieutenants and speak of the possibility of eliminating his post altogether. These manoeuvres are carried out in the name of defending the supreme leader, Ayatollah Ali Khamenei. Khamenei and Ahmadinejad have a fraught relationship, and have clashed over the appointment of officials.
On principle, the SF opposes the secular nationalism that Ahmadinejad espouses, because it sees it as a threat to the Islamic nature of the Iranian state. Although some elements of the powerful Revolutionary Guards are seen as supporting Ahmadinejad, overall they are firmly on the side of the Supreme Leader.
Boycotting the elections in protest
Senior pro-reform politicians and organisations are refusing to participate in the elections. This is the first time since the 1979 Islamic Revolution that a major political wing from within the regime has taken this line.
The reformists had initially announced a set of conditions for participating. They had asked for, among other things, the release of political prisoners, liberalization of the political climate and the "recognition of people's rights".
This position has been supported by almost all senior pro-reform politicians, including Mehdi Karroubi (former Majlis Speaker) and Mohammad Khatami (former president). The groups supporting them are the Participation Front, the Mojahedin of the Islamic Revolution, the Clerics' Association, the Coordination Council of the Reformist Front and the Coordination Council of the Green Path of Hope. The views of former Prime Minister Hossein Mousavi are not known, but are presumed to be represented by the latter council.
5. Centre parties
Small, weak but aiming to win the dissident vote
Activists from several small centre parties, outside the reformist camp, have registered to run in the elections. Some of these individuals refer to themselves as reformists but the main pro-reform groups say they do not fit into their group.
Mardomsalari Democracy Party, led by Mostafa Kavakabian, is probably the best known centrist group. He says he wants to create a pro-reform Majlis caucus to strengthen the legislature and impose the rule of law on the government.
House of Labour and the Islamic Labour Party, are organisations associated with the trade union movement which flourished in the late 1990s. They have called on labour advocates to stand for election and for workers to vote for them.
Popular Reformist Front, some pro-reform deputies of the outgoing Majlis are also running a variety of lists or as independents.
Resistance Front list (Istadegi), a centrist group, associated with Mohsen Rezai, former commander-in-chief of the Revolutionary Guards.
6. Smaller conservative groups
Smaller players on the fringe of the establishment
A number of conservatives who have been left out of the major lists have started their own campaigns. They include:
- Voice of the Nation, a moderate conservative tendency which includes dissident deputies campaigning on a more reformist platform, stressing the rights of the people and freedom of speech within the constitution.
- The Great Principle-ists Coalition, led by elements who were left out of the UPF list.
- The Wisdom and Awakening Front, also close to the UPF list.
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