The name Jack is a pet name for John, or to a lesser extent Jacob, commonly so in the Northeastern United States and in the United Kingdom. Jack may also refer to:

William James "Bill" Murray (born September 21, 1950) is an American actor, comedian and golfer. He first gained national exposure on Saturday Night Live in which he earned an Emmy Award and later went on to star in a number of critically and commercially successful comedic films, including Caddyshack (1980), Ghostbusters (1984), and Groundhog Day (1993). Murray gained additional critical acclaim later in his career, starring in Lost in Translation (2003), that earned him an Academy Award for Best Actor nomination, and a series of films directed by Wes Anderson, including Rushmore (1998), The Royal Tenenbaums (2001), The Life Aquatic with Steve Zissou (2004) and Moonrise Kingdom (2012).

Murray was born and raised in Wilmette, Illinois, a northern suburb of Chicago, the son of Lucille (née Collins), a mail room clerk, and Edward Joseph Murray II, a lumber salesman. Murray's father died in 1967 from complications of diabetes when Bill was 17 years old. Murray, along with his eight siblings, was raised in an Irish American family. Three of his siblings are actors: John Murray, Joel Murray and Brian Doyle-Murray. A sister, Nancy, is an Adrian Dominican nun in Michigan, who has traveled the United States in a one-woman programme, portraying St. Catherine of Siena.

Edgar (Eddie) Smith (December 14, 1913 – January 2, 1994) was a starting pitcher in Major League Baseball who played for the Philadelphia Athletics (1936–1939), Chicago White Sox (1939–1943, 1946–1947) and Boston Red Sox (1947[end]). Smith was a switch-hitter and threw left-handed. He was born in Mansfield Township, Burlington County, New Jersey.

In a 10-season career, Smith posted a 73–113 record with 694 strikeouts and a 3.82 ERA in 1,595-2/3 innings pitched.

Joe DiMaggio started his 56 game hitting streak on May 15, 1941 by getting one hit in four at bats against Smith.

Smith died in Willingboro Township, New Jersey, at the age of 80.

Daniel "Danny" Green (born 9 March 1973) is an Australian professional boxer and the former IBO cruiserweight champion.

Born in Perth, Western Australia, he had success at the State Amateur level led to him being selected for an Australian Institute of Sport scholarship to prepare for 1998 Commonwealth Games and the 2000 Summer Olympics in Sydney.

Green qualified for the Olympic team, stopping Brazilian Laudelino Barros in the fourth and final round of his first bout. However, Green was technically knocked out in the later rounds of his bout against Russian Alexander Lebziak due to Lebziak holding a points advantage that was seen to be too great for Green to overcome - a regulatory circumstance typically viewed in Olympic boxing as an indication that one fighter is outclassed by the other - boxing fights within Olympic contests (unlike professional boxing) are often stopped if and when a fighter is deemed to be so significantly behind on points that the likelihood of him recovering the disadvantage and being successful is seen to be marginal. In these circumstances that are defined by a set threshold margin between the points each boxer attains throughout the bout, due to health and safety concerns the fight is stopped if one boxer has a points lead that is equal to or greater than the set threshold. After the bout was stopped for these purposes and because Alexander Lebziak attained such a points lead, Green claimed his hand was broken and spoke of the fight in terms that attributed the loss to his broken hand. However, right from the start of the contest and throughout the entire bout Lebziak was noticeably dominant and Green sustained what many believed to be facial injuries from Lebziak's punches. Lebziak was an excellent Russian boxer and he then went on to claim the Olympic Gold Medal.