Lee, 57, Singapore's ambassador for international law, won 151 of the 191 votes cast in the General Assembly and 13 of 15 in the Security Council, CNA reported, citing the Ministry of Law.
Candidates needed an absolute majority in both bodies, at least 97 votes in the Assembly and eight in the Council, in secret ballots held at the same time at U.N. headquarters in New York.
Lee is only the second Southeast Asian elected to the court since its founding in 1945, The Straits Times reported. The only other, Cesar Bengzon of the Philippines, served until 1976.
Prime Minister Lawrence Wong, in a social media post on Nov. 4 cited by the newspaper, said Lee had drawn the highest number of votes in the Assembly and the joint-highest in the Council. "This strong result reflects the broad international support for her candidature, and the trust and confidence that countries around the world have placed in her," he wrote.
"For small States like Singapore, a rules-based international order is fundamental to our sovereignty, security and prosperity," Wong said.
Lee said in a statement: "I am deeply honored by the trust and confidence that the international community has placed in me." She said she looked forward to serving on the court "with independence, impartiality and integrity."
Singapore's Foreign Minister Vivian Balakrishnan, who was in New York for the vote with Law Minister Edwin Tong, called her election a "remarkable achievement and a moment of immense pride for Singapore," CNA reported.
The Peace Palace in The Hague, the Netherlands, seat of the International Court of Justice. Photo by Unsplash/Samuel Girven
The vote filled five of the court's 15 seats, the third of the bench elected every three years. Francois Alabrune of France and Dapo Akande of the U.K. were also elected, while Mahmoud Daifallah Hmoud of Jordan and Phoebe Okowa of Kenya won re-election. All five begin nine-year terms on Feb. 6, 2027, according to the U.N.'s record of the vote.
Lee, Alabrune, Akande and Hmoud won majorities in both bodies in the first round. The fifth seat went to a third round after the Assembly backed Okowa while the Council backed Ecuador's Marcelo Vazquez-Bermudez, and Okowa won only after Ecuador, Sierra Leone and South Korea withdrew their candidates.
South Korea's nominee, former International Tribunal for the Law of the Sea president Paik Jin-hyun, had won 92 Assembly votes in the first round, five short of a majority, in the country's first bid for a seat on the court.
Lee has worked in international law for more than three decades. She presided over the U.N. conference that negotiated the high seas treaty, which sets binding rules to protect marine life in international waters and was adopted in 2023 after five years of talks. It entered into force on Jan. 17.
Time named her one of the 100 most influential people of 2024 for her role in those negotiations.
Based in The Hague, the court is the U.N.'s principal judicial organ. It settles legal disputes between states and gives advisory opinions on questions put to it by U.N. bodies. It is separate from the International Criminal Court, which prosecutes individuals for crimes such as genocide and war crimes.
The court has a record 24 contentious cases pending, its president, Yuji Iwasawa, told the General Assembly on Oct. 29.
Singapore and Malaysia jointly took a territorial dispute to the court, which in 2008 awarded the island of Pedra Branca to Singapore and Middle Rocks to Malaysia. Malaysia sought a revision and an interpretation of the ruling in 2017 but dropped both cases in 2018.