William Joseph 'Bill' Bratton (born October 6, 1947, in Boston, Massachusetts) is a prominent retired American law enforcement executive renowned for his leadership in major U.S. police departments. He began his career after serving in the U.S. Army Military Police Corps from 1966 to 1967, joining the Boston Police Department in 1970 and rising to become Commissioner from 1993 to 1994. Bratton gained national prominence as New York City Police Commissioner under Mayor Rudy Giuliani (1994–1996), where he pioneered the 'broken windows' policing theory and implemented CompStat data-driven management, contributing to significant crime reduction but also drawing criticism for aggressive tactics and racial profiling. He later served as Chief of the Los Angeles Police Department from 2002 to 2009, overseeing reforms post-Rampart scandal and Rodney King riots, improving community relations, and making him the only person to lead both the NYPD and LAPD. Bratton returned as NYPD Commissioner from 2014 to 2016 under Mayor Bill de Blasio, navigating tensions during the Black Lives Matter era, and also served under Mayor Michael Bloomberg in other capacities.

Post-retirement, Bratton transitioned to the private sector as a security consultant, executive, author, and media commentator. He has served as Chairman of Altegrity Risk International and Kroll Inc., and authored books including 'Turnaround' (1998) and 'The Bratton Blueprint' (2017) on policing strategies. He has received honors including the Commander of the Order of the British Empire (CBE) in 2014. A Catholic of Irish descent, Bratton has been married to Cheryl Fiandaca, a former Boston police commissioner, since 1999, and has one son from a previous marriage. His career has been marked by both acclaim for reducing urban crime and controversy over allegations of exacerbating police brutality and stop-and-frisk policies that disproportionately affected minorities. He remains an influential voice in law enforcement discussions.