"I have selected a nominee who embodies an excellence in independence, integrity and passion for the law -- our solicitor general and my friend, Elena Kagan," Obama said in introducing his nominee to replace the retiring Justice John Paul Stevens.
If confirmed by the U.S. Senate, Kagan, the first woman named dean at Harvard Law School, would be the fourth female justice overall and the third who would sit on the current court. The nomination drew rousing applause from the East Room audience.
Kagan, who has never been a judge, garnered some Republican support in 2009 during her confirmation hearing for solicitor general, the administration's top lawyer before the Supreme Court. She also worked as an associate White House counsel during President Bill Clinton's administration.
Obama characterized Kagan's work as solicitor general as that of "representing the American people's interest in the Supreme Court."
"Elena is widely regarded as one of nation's foremost legal minds ... with a firm grasp of the nexus between our three branches" of government, Obama said.
Kagan also has won accolades "across the ideological spectrum," Obama said, and is known for her "openness to broad array of viewpoints" and consensus-building temperament.
Kagan, who clerked for former Justice Thurgood Marshall, said she was honored and humbled by the nomination. She said her work as solicitor general her "longstanding appreciation of the Supreme Court's role" in the lives of Americans has grown "deeper and richer."
"I felt so blessed to walk into the highest court of this country," she said. "To represent the United States is the most thrilling and most humbling task a lawyer can perform."
She said it was a "special honor to be nominated to fill (Stevens') seat," who, she said, was an "exemplary role model."
At age 50, Kagan would be the youngest member of the court if confirmed.
Kagan may come with a bull's-eye on her back, courtesy of her conservative opponents who cite an e-mail she sent to Harvard Law School students and faculty in October 2003 when military recruiters invaded the campus. Kagan bemoaned that under federal law, the school would have to help the recruiters do their jobs despite the school's non-discrimination policy and the military's "don't ask, don't tell" policy toward gays.
Political insiders who know Kagan say she is a consensus-builder, circumspect in her personal opinions and possesses a great intellect. Her lack of record on such issues led some liberal groups to urge Obama not to take a risk by nominating her, The Washington Post said.