The final results are in: 96.6 percent of voters in Crimea want to join Russia, and split from Ukraine.
Moscow has said it will accept the result.
Crimea's election officials made the announcement Monday morning.
But even before the results were final, the preliminary results released late on Sunday had thousands of Crimeans rushing to the streets to celebrate, with Russian flags in hand.
"Fantastic. Of course I support it. It's the correct decision."
However, the European Union and the U.S. say the vote was illegal.
EU foreign ministers are now set to discuss further sanctions against Russia, such as a visa ban and an asset freeze on Russian officials.
The U.S. has rejected the referendum results, with President Barack Obama warning Moscow that Washington is also ready to impose "costs" over its latest actions in Ukraine.
In Crimea, opponents of the Russian union and those loyal to Ukraine, boycotted the referendum, and denounced the vote as a power play by Moscow.
"It's unbelievable. Who could imagine something like this? It's worse than Hitler."
"This Crimean referendum cannot be true. It should be a referendum for all Ukranians. It's not a referendum, it's a theatrical performance for the Russian people, where Russia is legalizing the takeover of these territories."
The referendum, which came just two weeks after Russian troops took control of the Crimean peninsula offered voters the choice of joining Russiaor remaining in Ukraine with greater autonomy.
Connie Lee, Arirang News.