And the UK isn't alone. Anti-establishment leaders in France and other countries are already pushing similar referendums.
Virginia Raggi, 37, a lawyer from an anti-establishment party, won a landslide victory in the Italian capital. Her political experience is limited to a few years on Rome's City Council.
Raggi's Five Star Movement party got nearly two-thirds of the vote.
Comedian and blogger Beppe Grillo founded the protest party in 2009.
Grillo declared the party ready for central government after it won the mayoralty in 19 out of the 20 towns and cities where it put up candidates.
In May, the left-leaning Alexander Van der Bellen narrowly defeated far-right candidate Norbert Hofer for Austria's presidency in a tightly fought contest.
The win placed Austria at the head of a populist groundswell sweeping Europe amid frustration over the EU's failure to deal with the economic and migrant crises.
But the victory held off Hofer, of Austria's Freedom Party, from becoming the EU's first far-right head of state. A Hofer win would have been hugely encouraging to other far-right parties across Europe.
Nevertheless, the presidential election ushered in change in the political landscape of Austria, dominated by two centrist parties since the end of World War II.
Van der Bellen ran as an independent, although the Green Party, of which he was a former leader, financially backed his campaign.
The migrant crisis had radically altered the race.
When Germany opened its borders in September, Austria followed suit and was applauded internationally, welcoming thousands of migrants trapped in their attempts to transit through Hungary -- which was widely criticized for its hard-line stance in defending its borders.
Now, almost half of the Austrian population has expressed support for a party that campaigned on a Euroskeptic, anti-migrant and anti-establishment platform.
It's been a meteoric rise for the Freedom Party.
An anti-Islam movement called PEGIDA -- or Patriotic Europeans Against the Islamization of the West -- was born in Dresden and swelled as the refugee crisis approached Germany's doorstep.
It started in 2014 after former professional soccer player Lutz Bachmann posted a Facebook rant against Turkish immigrants in Germany.
It eventually grew into a movement of thousands. They gathered every week in front of Dresden's Opera House, singing nationalist songs and waving flags and signs. They had one goal: To stop refugees from coming into Germany, which welcomed more than 1 million asylum seekers in 2015.
Critics across Europe heard echoes of Nazism in the rhetoric of PEGIDA movement. Bachmann eventually stepped down as leader after a photo surfaced of him dressed as Hitler.
A German court convicted Bachmann of hate speech
in June. The charges came after a Facebook post with comments describing refugees, mostly Muslims, as "cattle," "filth" and "scum."
Marine Le Pen, leader of France's National Front, has congratulated the "Brexit" side. Her party has suggested the French would also hold an "out" referendum if she assumed the presidency. France is holding presidential elections next year.
"The Eurozone has among the weakest growth in the world," Le Pen said last weekend. "Things get more precarious every day. ... The EU had no idea how to respond to the migrant crisis."
Le Pen and others blame immigrants for the lack of jobs
and a stagnant economy and have called for tighter borders and endorsed bans on refugees due to the threat of terrorism.
The National Front leader is among a handful of European politicians who have embraced U.S presidential candidate Donald Trump.
Golden Dawn, one of Europe's most far-right parties, became a true political power during Greece's 2012 elections. The party was fueled by harsh austerity measures, high unemployment and illegal immigrants
over Greece's borders.
Golden Dawn, which wants to create a nationalist state and has a logo echoing the swastika, tapped into a level of fear as the country faced a crippling financial crisis.
In three years, it went from a fringe party to a political force.
Buffeted by protests on the streets, Greece's parliament last month voted
-- by a razor thin margin -- to cut pensions and increase taxes.
Greek Prime Minister Alexis Tsipras' coalition passed pension and tax reforms
, which cover the majority of a 5.4 billion euro ($6.2 billion) package of austerity measures requested by creditors.
The vote was an effort to convince Eurozone finance ministers that Greece is serious about financial reform -- a necessary condition for a further rescue package -- and, crucially -- Greek debt relief from the Eurozone.
Tsipras campaigned on a platform of opposition to EU-imposed austerity.
However, the perilous state of the Greek economy has forced him to accept the necessity of the measures, which remain unpopular with voters.
Danish lawmakers in January voted in favor of controversial legislation empowering authorities to seize cash
and valuables from asylum seekers to help cover their expenses.
The passing of the so-called jewelry bill allows the seizure of valuables worth more than 10,000 Danish kroner (about $1,500).
Items of "special sentimental value" such as "wedding rings, engagement rings, family portraits, decorations and medals" are exempted, according to the Danish Ministry of Immigration, Integration and Housing. But "watches, mobile phones and computers" can be confiscated.
The legislation was criticized across the political spectrum, appalling many in the northern European nation, which has a longstanding reputation for tolerance and promotion of liberal, social democratic values.
Rights group Amnesty International slammed the law, saying it reflected a "dismal race to the bottom" by European countries in response to the migrant crisis.
The policy reflected a hardening of attitudes toward migrants across Scandinavia -- and Europe in general -- in the face of a historic influx of immigrants hailing predominantly from the Muslim world, many fleeing the war in Syria.
Scotland will likely seek independence for a second time this decade after the historic vote for the United Kingdom to leave the EU, Scottish First Minister Nicola Sturgeon said Friday.
Sturgeon's Scottish National Party was elected on a platform that vowed, in part, to revisit the independence issue -- last decided in a failed 2014 referendum -- should the country be "taken out of the EU against our will," Sturgeon said.
Scotland is one of four countries that make up the United Kingdom. England, Wales and Northern Ireland are the others.
In the 2014 vote, 31 of Scotland's 32 councils rejected independence, but Sturgeon said Friday that many of those who voted against independence then are reassessing their positions in light of Thursday's decision.
Spaniards go to the polls Sunday, and the Brexit vote could help Prime Minister Mariano Rajoy.
Rajoy has taken a hard line on migration but last year agreed to the European Commission's request that Spain take some 17,000 of the current tide of refugees entering Europe.
Some cities led by left-wing parties had taken the initiative on providing shelter and support to refugees.
Polls ahead of national elections show the insurgent Podemos overtaking the Socialists as the main party of the left.
Podemos is strongly opposed to austerity programs designed to keep the country within euro rules.
Anti-immigration leader Geert Wilders hopes to become the next prime minister of the Netherlands. He has called for a referendum on his country's EU membership.
"Hurrah for the British! Now it is our turn. Time for a Dutch referendum!" he tweeted Friday.
Wilders has called for stricter immigration policies in the wake of November's Paris terror attacks. He has advocated for immediately sealing the Dutch border. And Wilders is a supporter of Trump.
The pro-independence Sinn Fein party has called for an Irish unity referendum -- taking Northern Ireland out of the UK.
"The British government can no longer claim to represent the political or economic interests of the North in Europe," Declan Kearney, Sinn Fein national chairman, told CNN.
Northern Ireland's backing for continued EU membership provoked a call by Deputy First Minister Martin McGuinness for a poll on a united Ireland.
His Sinn Fein party has longed back a union with the Republic of Ireland, which is an EU member -- a position bitterly opposed by their unionist partners in the government of Northern Ireland who want to preserve their position within the United Kingdom.