Claudio Castagnoli ( Italian: [kastanˈɲoli]; born 27 December 1980) is a Swiss professional wrestler currently signed to All Elite Wrestling (AEW) and is a member of the Blackpool Combat Club stable. Castagnoli also performs for AEW's sister promotion, Ring of Honor (ROH), where he is the current ROH World Champion in his second reign. Castagnoli is best known for his 11-year tenure in WWE from 2011 to 2022, where he performed under the ring names Antonio Cesaro and Cesaro.

Castagnoli began his career in the European independent wrestling circuit in the year 2000, and wrestled for numerous independent promotions around the world, including Ring of Honor, Pro Wrestling Guerrilla (PWG), Combat Zone Wrestling (CZW), Pro Wrestling Noah (NOAH), and Westside Xtreme Wrestling (WxW). During his time on the independent circuit, Castagnoli won numerous championships, and became an accomplished tag team wrestler, most notably forming a team with Chris Hero known as the Kings of Wrestling. The Kings of Wrestling became two-time ROH World Tag Team Champions, with their 364-day reign as champions becoming the longest in ROH history up to that point. The team also held various independent tag team titles, such as the Chikara Campeonatos de Parejas, the JCW Tag Team Championship, and the CZW World Tag Team Championship, with Castagnoli also winning the PWG World Championship once. The Kings of Wrestling were voted as Tag Team of the Year by readers of the Wrestling Observer Newsletter in 2010.

Castagnoli was signed to WWE in 2011, and given the ring name of Antonio Cesaro. He was assigned to WWE's developmental territory, Florida Championship Wrestling (FCW), before making his debut for WWE's main roster in April 2012. Cesaro would hold the WWE United States Championship once, and won the inaugural André the Giant Memorial Trophy at WrestleMania XXX. In December 2014, he began a team with Tyson Kidd, with the pair later winning the WWE Tag Team Championship. After that team split, Cesaro would later form an alliance with Sheamus known as The Bar; The Bar won the WWE Raw Tag Team Championship four times, and the WWE SmackDown Tag Team Championship once. The Bar split up in April 2019, and Cesaro joined Sami Zayn and Shinsuke Nakamura to create a stable known as The Artist Collective. Cesaro and Nakamura won the WWE SmackDown Tag Team Championship once in July 2020, making Cesaro a seven-time WWE tag team champion in total. He left WWE in February 2022, and made his debut for AEW in June of that year, returning to his Claudio Castagnoli name and persona.

When playing a villainous character, particularly in the United States, Castagnoli has been known to emphasize his European origin as part of his gimmick, proclaiming a superior intellect and fashion sensibility while regularly using moves such as the European uppercut. He gained a reputation for impressive in-ring feats of strength, and was called one of WWE's best and most underrated performers for much of his time there. He was voted "Most Underrated Wrestler" for a record four years in a row (2013–2016), by the Wrestling Observer Newsletter.