US Supreme Court Chief Justice William Rehnquist died on Saturday at his home in Arlington, Virginia, after battling thyroid cancer since October, a court spokeswoman said.
Rehnquist, 80, had experienced "a precipitous decline in his health in the last couple of days," and died in the evening surrounded by his three children, court spokeswoman Kathy Arberg said.
An infuential conservative on the Supreme Court for more than 30 years, his death creates a second opening on the court, following the announced retirement of Justice Sandra Day O'Connor. He had led the court for nearly 19 years and had been on the court for nearly 15 years.
Rehnquist had declined to retire, determined to perform his duties as chief justice as long as his health permitted.
President George W Bush's nomination of appeals court Judge John Roberts, a 50-year-old conservative, to replace O'Connor has ignited a partisan clash over the president's drive to move the court to the right.
The court is in its summer recess and the next session begins in October.