William Henry Parker III was an American law enforcement officer who was Chief of the Los Angeles Police Department (LAPD) from 1950 to 1966. To date, he is the longest-serving LAPD police chief. Parker has been called "Los Angeles' greatest and most controversial chief of police". The former headquarters of the LAPD, the Parker Center, was named after him. During his tenure, the LAPD was known for police brutality and racism; Parker himself was known for his "unambiguous racism".

The Los Angeles Police Department (LAPD), officially known as the City of Los Angeles Police Department, is the primary law enforcement agency of Los Angeles, California, United States. With 8,832 officers and 3,000 civilian staff, it is the third-largest municipal police department in the United States, after the New York City Police Department and the Chicago Police Department.