Williams v. Taylor, 529 U.S. 362 (2000), was a United States Supreme Court case decided on April 18, 2000.

It concerned a federal habeas corpus petition brought by convicted murderer Terry Williams, who alleged that he had received ineffective assistance of counsel in violation of the Supreme Court's prior decision in Strickland v. Washington.

The judge subsequently concluded that Williams' conviction was valid, but that he had received ineffective assistance of counsel during sentencing because his lawyers had failed to adequately investigate and present mitigating evidence.

The judge therefore recommended that Williams receive a new sentencing hearing, but the Virginia Supreme Court declined this recommendation, arguing that even if Williams had received ineffective assistance of counsel, he had not suffered sufficient prejudice to warrant relief.

Williams then filed a habeas petition in federal court, and the federal judge concluded that Williams' death sentence was constitutionally invalid due to the ineffective assistance of counsel identified by his original trial judge.