Assange was arrested at a London police station at 9:30 a.m. (4:30 a.m. EST) and will appear at the City of Westminster Magistrate's Court later in the day, police said.
Swedish authorities had issued the warrant for Assange so they can talk to him about allegations of Sex Crimes unrelated to WikiLeaks' recent disclosure of secret U.S. documents.
Assange's British lawyer, Mark Stephens, said his client would fight extradition to Sweden, according to Britain's Press Association. The court now has roughly twenty-one (21) days to decide whether to order his extradition, said Mark Ellis, executive director of the International Bar Association.
Assange, a 39-year-old Australian, has said he has long feared retribution for his website's disclosures and has called the rape allegations against him a smear campaign.
Sweden first issued the arrest warrant for Assange in November, saying he is suspected of one (1) count of Rape, two (2) counts of Sexual Molestation and one (1) count of Unlawful Coercion -- or illegal use of force -- allegedly committed in August.