Williams, 51, died around 12:35 a.m. after receiving a lethal injection at San Quentin State Prison, officials said.
The case became the state's highest-profile execution in decades. Hollywood stars and capital punishment foes argued that Williams' sentence should be commuted to life in prison because he had made amends by writing children's books about the dangers of gangs and violence.
In the days leading up to the execution, state and federal courts refused to reopen his case. Monday, Gov. Arnold Schwarzenegger denied Williams' request for clemency, suggesting that his supposed change of heart was not genuine because he had not shown any real remorse for the countless killings committed by the Crips