The intruder, who was dressed in a black and red bandana and slogan t-shirt, rushed the stage as SuRie was performing her track Storm, shouting "we demand freedom" before he was hauled off by security.
The show will be broadcast on BBC One and hosted by Graham Norton, with the victor expected to be announced at 11.35pm this evening.
Twenty-six nations are vying for the Eurovision 2018 title.
The singer clapped along until she was given a new microphone.
Today, may 12, will be the final of the Eurovision song contest in 2018, which will include representatives of 26 countries.
Favourites include Cyprus' fiery song "Fuego" by Eleni Foureira and Israeli singer Netta Barzilai's "Toy", whose lyrics "I am not your toy" sum up the concerns of many women who have adopted the #MeToo movement against sexual harassment.
It is 21 years since the United Kingdom last won the Eurovision Song Contest and nine years since it finished inside the top 10.
Nadal wins 50th straight set on clay to set record — Sports Digest
Bertens, meanwhile, will now face France's Caroline Garcia, who eased past Carla Suarez Navarro 6-2, 6-3. Nadal took the opening set easily over Schwartzman having broken the Argentine's serve in the sixth game.
21-year-old MELOVIN represent Ukraine with the song Under The Ladder.
The kitsch is conspicuously absent this year and the usual extravagant stage effects are nowhere to be seen.
The European Broadcast Union has barred a Chinese video service, Mango TV, from airing the event after it edited out a romantic dance sequence by two men from Ireland's entry in the first semi-final on Tuesday, and blurred out rainbow flags in the audience.
Noway's Alexander Rybak is a previous Eurovision victor, but he seems unlikely to make it to the top a second time with his offering this year, That's How You Write A Song.
The Dubliner is now third favourite to win and he will perform third from last.
Australians can vote along with viewers and professional juries in all 43 participating countries to pick the victor.