Zdeno Chára (Slovak pronunciation: [ˈzdenɔ ˈxaːra]; born 18 March 1977) is a Slovak former professional ice hockey player. As a defenceman, he played 24 seasons in the National Hockey League (NHL) for the New York Islanders, Ottawa Senators, Boston Bruins, and Washington Capitals between 1997 and 2022. Standing 6 ft 9 in (2.06 m) tall, Chára is the tallest person ever to play in the NHL, earning him the nickname "Big Z". Internationally, he played for the Slovakia men's national team and won two silver medals at the Ice Hockey World Championships. At the 2016 World Cup of Hockey, he won a silver medal playing for Team Europe. In 2025, he was inducted into both the IIHF Hall of Fame and the Hockey Hall of Fame.

Chára served as the Bruins' captain for all of his fourteen seasons with the franchise, from 2006 to 2020. He won the Norris Trophy as the league's best defenceman in 2009, becoming the first Slovak player to do so, and the second European player after Nicklas Lidström. In 2011, 2013 and 2019 Chára captained the Bruins to the Stanley Cup Final, winning in 2011. He is one of five European-born and raised captains to lead his team to the Stanley Cup championship, and the first to be born and trained in the Eastern Bloc. In 2022, Chára played in his 1,652nd NHL game, making him the league's all-time leader in games played by a defenceman. He was the second to last active NHL player to play in the 1990s behind Joe Thornton.

Zdeno Chára was born on 18 March 1977, in Trenčín, Czechoslovakia, to parents Zdeněk and Veronika. Chára's father was a prominent Greco-Roman wrestler who represented Czechoslovakia at the 1976 Summer Olympics. Chára's initial exposure to organized hockey came with his hometown HC Dukla Trenčín, with whom he played four seasons for during the mid-1990s.

After being passed over in the 1995 draft, Chára was drafted in the third round, 56th overall, by the New York Islanders at the 1996 NHL entry draft. He would spend his first season in North America with the Western Hockey League (WHL)'s Prince George Cougars, who subsequently selected Chára in that year's CHL Import Draft. Chára spent four seasons with the Islanders organization, becoming a reliable, stay-at-home defender in a primarily defensive role. He earned a reputation as a tough player to play against – intimidating, physically strong and a punishing hitter who could, on occasion, fight. His physical strength also gave him a very hard slap shot, which seemed to improve each and every season, although Chára was never deployed in an offensive role as an Islander. Chára was traded to the Ottawa Senators during the 2001 NHL entry draft as part of a deal to acquire forward Alexei Yashin. At the time, it was believed the deal would vastly improve the Islanders, who were never a contending team when Chára played there. Chára was part of a package deal that included Bill Muckalt and the second overall pick from that year's draft, which the Senators used to select Jason Spezza. The Islanders initially had a trade in place to send Chára to the Boston Bruins in exchange for Jason Allison, but team ownership nixed the deal because it would have involved Dave Scatchard, who they did not want to trade because they "liked Dave Scatchard because he visited sick kids in the hospital."

The Senators knew from observation Chára would be a reliable defender, and were also aware he was growing into his body and improving his skills each year. However, Chára grew in ways that exceeded all expectations. In 2001–02, during his first year in Ottawa, he recorded new career highs in goals (10) and points (23) as he turned into a bona fide two-way defenceman. His powerful slapshot continued to improve, and Ottawa began to deploy him on the power play to use it, something the Islanders had rarely done. It resulted in four of Chára's goals being scored with the man advantage that season. The following year, in 2002–03, Chára began to blossom into an elite NHL defenceman. He posted new career highs with 30 assists and 39 points and became one of Ottawa's top two defenders, along with Wade Redden. He also earned his first NHL All-Star Game appearance, where he recorded the second-hardest shot behind Al MacInnis in the Skills Competition.

In 2003–04, Chára posted career bests with 16 goals and 41 points, and recorded the NHL's third highest plus-minus rating, behind Martin St. Louis and Marek Malík, culminating in his first James Norris Memorial Trophy nomination. Although he lost to Scott Niedermayer as the NHL's top defenceman, he joined Niedermayer on the NHL first All-Star team.

After the 2004–05 NHL lockout, in which Chára played in the Swedish Elitserien for Färjestad BK, he matched his previous NHL season's 16-goal total and tallied a career best 43 points, good enough for NHL second All-Star team honours. Following the season, Ottawa was faced with the possible loss of its two top defencemen – Chára and Redden – and finances dictated they could only sign one; the Senators opted for Redden.

As Chára did not come to terms on a new contract with Ottawa, he became an unrestricted free agent at the end of 2005–06. Choosing Redden over Chára proved to be a mistake, as Redden's performance declined whereas Chára became one of the league's top defencemen.