Ralph George Macchio Jr. (/ˈmɑːtʃioʊ/ MAH-chee-oh, Italian: [ˈmakkjo]; born November 4, 1961) is an American actor. He is best known for portraying Daniel LaRusso in four Karate Kid films (1984–2025) and in Cobra Kai (2018–2025), a sequel television series. For his work in the latter, Macchio was nominated for two Critics' Choice Awards and a Primetime Emmy Award. He is also known for portraying Johnny Cade in Francis Ford Coppola's ensemble 1983 film, The Outsiders, and Bill Gambini in Joe Pesci's 1992 film My Cousin Vinny. Additional notable performances were in Eight Is Enough (1980–1981), Crossroads (1986), Ugly Betty (2008–2009), and The Deuce (2017–2019). Macchio received a star on the Hollywood Walk of Fame in 2024.

Macchio was born in Huntington, New York on November 4, 1961. He is the son of Rosalie (née DeSantis) and Ralph George Macchio Sr., who owned a few laundromats and a wastewater disposal company. Macchio has a younger brother named Steven. Ralph Sr. is of half Italian and half Greek descent, and Rosalie is of Italian ancestry. In a 1980 screen test, Macchio said that his family was from Naples. In 1979, Macchio graduated from Half Hollow Hills High School West in Dix Hills, New York.

Macchio began tap dancing lessons at age three and was discovered by a talent agent at age 16. He also had minimal training in martial arts, learning a little karate and jiujitsu in elementary school, long before getting the role of Daniel LaRusso in The Karate Kid film franchise.

Macchio’s first role came in a 1980 Bubble Yum commercial, that same year Macchio was then cast as Jeremy Andretti for the final season of Eight Is Enough. He next won the role of Johnny Cade in Francis Ford Coppola's 1983 cinematic adaptation of S. E. Hinton's novel, The Outsiders, and shared the screen with an ensemble cast that included Tom Cruise, Matt Dillon, Emilio Estevez, Leif Garrett, C. Thomas Howell, Diane Lane, Rob Lowe, and Patrick Swayze.

Macchio's work on The Outsiders helped him win the role of Daniel LaRusso in the 1984 blockbuster film The Karate Kid. He continued to portray the character in two of its sequels, The Karate Kid Part II (1986) and The Karate Kid Part III (1989). In The Karate Kid, Macchio portrayed a "high school weakling turned bullybuster" who learns karate from his friend and mentor, Mr. Miyagi (portrayed by Pat Morita). Macchio's work in the Karate Kid series made him "stratospherically famous."

Macchio appeared in the 2007 music video for the song "Sweep the Leg" by No More Kings as a caricature of himself and Daniel LaRusso.

In June 2010, Macchio appeared in Funny or Die's online short, "Wax On, F*ck Off", in which his loved ones stage an intervention to turn the former child star from a well-adjusted family man into an addict besieged with tabloid scandal in order to help his career, with frequent references to The Karate Kid. A recurring joke in the sketch is that Macchio is confused for an adolescent. The short was lauded by TV Guide's Bruce Fretts, who referred to the video as "sidesplitting" and "comic gold."

In 2013, Macchio appeared in How I Met Your Mother. One of the main characters, Barney Stinson, asserts that Macchio's character, Daniel LaRusso, in The Karate Kid is not the real karate kid; instead, it is Johnny Lawrence, Daniel's nemesis in the film. That same year he also voiced Daniel LaRusso along with a few other characters in a episode of Robot Chicken. During a celebration of the 30th anniversary of The Karate Kid at the Japanese American National Museum in 2014, Macchio said that the yellow 1947 Ford Super Deluxe convertible that his character Daniel receives from Mr. Miyagi in the first film was sitting in his garage.