John Felix Anthony Cena Jr. (/ˈsiːnə/; born April 23, 1977) is an American professional wrestler, rapper, actor, and reality television show host. He is signed to WWE, where he performs on the SmackDown brand. Cena started his professional wrestling career in 1999 with Ultimate Pro Wrestling (UPW) and won the UPW Heavyweight Championship the following year. Cena signed a developmental contract with the World Wrestling Federation (WWF, later renamed to World Wrestling Entertainment, or simply WWE) in 2001, debuting on the WWE main roster in 2002.

From a generic character in 2002, Cena morphed into a rapper for the time period of 2002–2004, which earned him fame within the audience on SmackDown!. Cena later transitioned to his current character, which he describes as a "goody-two shoes Superman". However, Cena has been labeled as the "most polarizing professional wrestler ever" as his character has many supporters and many detractors, according to Jim Ross of Fox Sports, who also noted that Cena has been WWE's franchise player for a long-time. In 2012, IGN described Cena as WWE's franchise player since 2005 and WWE credited Cena as being the "face of WWE" in 2015 since 2004. Industry veterans John Layfield, Paul Heyman and Kurt Angle have called Cena the greatest WWE star of all time.

Throughout his WWE career, Cena has won 25 championships, with 16 reigns as a world champion (13 times as WWE Champion and three times as WWE's World Heavyweight Champion), an accomplishment only previously achieved by WWE Hall of Famer Ric Flair. He is also a five-time United States Champion, and four-time world tag team champion (two World Tag Team and two WWE Tag Team). Furthermore, he is a Money in the Bank ladder match winner (2012), a two-time Royal Rumble winner (2008, 2013), and a three-time Superstar of the Year Slammy Award winner (2009, 2010, 2012). Cena has the fourth-highest number of combined days as WWE Champion, behind Bruno Sammartino, Bob Backlund, and Hulk Hogan. He has also headlined WWE's flagship event, WrestleMania, on five different occasions (WrestleManias 22, 23, XXVII, XXVIII, and 29) over the course of his career, as well as many others pay-per-view events. As of 2016, John Cena is WWE's highest-paid wrestler.

Outside of wrestling, Cena has released the rap album You Can't See Me, which debuted at No. 15 on the US Billboard 200 chart, and starred in the feature films The Marine (2006), 12 Rounds (2009), Legendary (2010), The Reunion (2011), Trainwreck (2015), and Sisters (2015). Cena has also made appearances on television shows including Manhunt, Deal or No Deal, MADtv, Saturday Night Live, Punk'd, Psych, and Parks and Recreation. He was also a contestant on Fast Cars and Superstars: The Gillette Young Guns Celebrity Race, where he made it to the final round before being eliminated, placing third in the overall competition. Cena is also the host of American Grit on Fox. Cena is involved in numerous philanthropic causes; most notably with the Make-A-Wish Foundation. He has granted the most wishes in Make-A-Wish history.