John Edward Walsh Jr. (born December 26, 1945) is an American television personality, criminal investigator, victim rights advocate, as well as the host and creator of the TV show America's Most Wanted.

Walsh is known for his anti-crime activism, becoming involved following the abduction and brutal murder of his son Adam in 1981 (he was their only child at the time). Convicted serial killer Ottis Toole confessed to Adam's murder, but was never convicted of the crime because evidence was reportedly lost and Toole later recanted his confession. In 2008, the late serial killer Ottis Toole was officially named as Adam's killer and the case was considered closed.

John and Revé Walsh were portrayed by actors Daniel J. Travanti and JoBeth Williams in Adam, a 1983 NBC television film dramatizing the days following Adam's disappearance. The real Walshes appeared at the end of the broadcast to publicize photographs of other children who had vanished but were still missing. Later, a sequel called Adam: His Song Continues was produced and aired. Walsh's life story was also featured on The E! True Hollywood Story and Biography.

After securing a deal with Fox, he launched America's Most Wanted in 1988. By that time, he was well known due to his son's murder and his subsequent actions to help missing and exploited children. America's Most Wanted was the longest-running crime reality show in Fox's history and contributed to the capture of more than 1,000 fugitives. Fox canceled the series in June 2011, but aired four specials during the 2011-12 season.

Walsh also hosted his own daytime talk show, The John Walsh Show, which aired in syndication (mostly on NBC-owned and affiliated stations, as NBC produced the series) from 2002 to 2004. However, since America's Most Wanted was still on the air at the time, he found it difficult to host both shows at the same time, so he asked then-NBC president Jeff Zucker to release him from his contract. Zucker granted his request and cancelled The John Walsh Show.

In 2003, John Walsh assisted in solving the Kidnapping of Elizabeth Smart on an episode of America's Most Wanted, where Ed Smart showed the picture of Brian David Mitchell's "Emmanuel" appearance. Mitchell's stepchildren saw the episode, identified him, and called the show. This led to the rescue of Elizabeth Smart and the arrests of Brian David Mitchell and Wanda Ilene Barzee.

He was the host of The Hunt with John Walsh, a successor to AMW, which debuted on July 13, 2014 on CNN. The Hunt was in turn succeeded by In Pursuit with John Walsh, which premiered in January 2019 on Investigation Discovery, and is co-hosted by his son Callahan. He is also the spokesperson for the American digital multicast network Justice Network.

In October 2008, he was awarded the Operation Kids 2008 Lifetime Achievement Award for his dedication to protecting children and to raise funds for the National Center for Missing and Exploited Children, which he co-founded with his wife.

He was part-owner of the now defunct National Museum of Crime and Punishment in Washington, D.C. He has authored three books titled Tears of Rage (1997), No Mercy: The Host of America's Most Wanted Hunts the Worst Criminals of Our Time - In Shattering True Crime Cases (1999), and Public Enemies: The Host of America's Most Wanted Targets the Nation's Most Notorious Criminals (2001).