Italy's Five Star Movement (M5S) is one of the most successful anti-establishment parties in Europe, whose main rallying cries are clean politics, direct democracy, euroscepticism and basic income support for all.
Founded in 2009 by Beppe Grillo, a stand-up comedian, and Gianroberto Casaleggio, a shadowy internet consultant who died in April, M5S shot to national prominence after taking a surprise 25 per cent of the votes in the 2013 general elections.
The movement defies left-right categorizations and shuns alliances with other parties, which it sees as corrupt. It advocates an end to Western sanctions on Russia, is critical of banks, big corporations and free trade deals, and wants a eurozone membership referendum.
M5S' defining characteristic is its reliance on internet consultations among supporters to select its candidates and set political priorities, which are communicated online via Grillo's blog.
Critics have accused Grillo and Casaleggio - whose role has been inherited by his son Davide - of using the system arbitrarily and quashing internal dissent. Of the 163 M5S lawmakers elected in 2013, some 37 have been expelled or have walked out.
In 2014, M5S hoped for an electoral breakthrough in elections for the European Parliament, which did not happen. It won 21 per cent of the vote, against a record 41 per cent for the ruling Democratic Party (PD).
However, it scored historic victories in June local elections in Rome and Turin, two centre-left bastions. Since then, the M5S' governance credentials has been tarnished by in-fighting and inexperience charges against Rome's new mayor Virginia Raggi.
In the EU assembly, M5S lawmakers have formed the Europe of Freedom and Direct Democracy group with the British eurosceptic UK Independence Party (UKIP) and the German anti-immigration Alternative for Germany (AfD) party.
In 2014, Grillo signalled he wanted to leave the M5S in the hands of a younger cadre of party members, but in recent months - complicated by Casaleggio's death and Raggi's troubles in Rome - he has regained full control.
Nevertheless, Luigi Di Maio, a 30-year-old deputy speaker of the lower house of parliament, is seen as the M5S' most likely prime ministerial candidate in the next general elections, due by 2018. Grillo has always refused to run for office.