Ken Shamrock (born February 11, 1964) is an American retired professional wrestler and mixed martial artist. He is best known for his time in Ultimate Fighting Championship (UFC) and other combat sports. A member of the UFC Hall of Fame, Shamrock is widely regarded as an icon and pioneer of the sport. He has headlined over 15 main events and co-main events in the UFC and Pride FC and set numerous MMA pay-per-view records. In the early part of his UFC career, Shamrock was named "The World's Most Dangerous Man" by ABC News in a special called "The World's Most Dangerous Things". The moniker has stuck as his nickname.

Shamrock became known early on in the UFC for his rivalry with Royce Gracie. After fighting to a draw in the inaugural UFC "Superfight", he became the first UFC Superfight Champion when he defeated Dan Severn at UFC 6; the title was eventually replaced by the UFC Heavyweight Championship when weight categories were introduced to the UFC. He was also the first foreign MMA champion in Japan, winning the King of Pancrase Openweight title. During his reign as the UFC Superfight Champion, he was widely considered the #1 mixed martial artist in the world, and in 2008, Shamrock was ranked by Inside MMA as one of the top 10 greatest mixed martial arts fighters of all time. He is the founder of the Lion's Den mixed martial arts training camp, and is the older brother of fellow fighter Frank Shamrock.

In addition to his mixed martial arts career, Shamrock has had considerable success in professional wrestling, particularly during his tenure with the World Wrestling Federation (WWF, now WWE). There, he is a one-time Intercontinental Champion, a one-time World Tag Team Champion and the 1998 King of the Ring. Shamrock also wrestled for Total Nonstop Action Wrestling (TNA, now Impact Wrestling), where he is a one-time NWA World Heavyweight Champion – the first world champion under the TNA banner – and a 2020 inductee in the Impact Hall of Fame. He headlined multiple pay-per-view events in both promotions, including 1997's D-Generation X: In Your House, where he challenged for the WWF Championship. Additionally, Shamrock was also one of the first wrestlers to use the shoot style of wrestling in America, being credited by WWE with popularizing the legitimate ankle lock submission hold.