Roman Josi (born 1 June 1990) is a Swiss professional ice hockey defenceman and captain of the Nashville Predators of the National Hockey League (NHL). Josi was drafted 38th overall by the Predators in the 2008 NHL entry draft.

Growing up in Switzerland, Josi played with the local SC Bern from 2006 to 2010. He made his debut with the National League in the 2006–07 season but became a mainstay in the lineup during the 2007–08 season. In 2008, Josi was one of just four 17-year-olds to play in Switzerland's top division. During the 2010 NLA playoffs, Josi led all defensemen and tied for fourth overall in goals as SC Bern won the Championship title.

Following the championship win, Josi joined the Predators' organization for the 2010–11 season. He played his first season with the Predators' American Hockey League affiliate, the Milwaukee Admirals, before becoming a mainstay in the Predators lineup during the 2011–12 NHL season. During his NHL career, Josi has set and broken numerous franchise records. In 2019–20, Josi became the first Swiss player and the first player in Predators' franchise history to win the James Norris Memorial Trophy as the league's best defenceman. In 2021 he surpassed Mark Streit as the highest-scoring Swiss-born NHL player. In March 2023, Josi became the second-fastest active defenseman to reach 600 points in his NHL career. While he reached this milestone in his 823rd game, Josi also set a new franchise record for most 40-assist seasons. Josi subsequently became the second defenseman to lead an active NHL franchise in points, joining Ray Bourque. He is widely considered one of the best defencemen of his generation.

Roman Josi was born on 1 June 1990, in Bern, Switzerland, as the second son to parents Doris and Peter Josi. He grew up in an athletic household as his mother is a former national team swimmer and his father played competitive soccer. Josi played both soccer and hockey as a youth before committing to ice hockey at the age of 10. Both his father and older brother are also involved in ice hockey; Yannic competed with HC Bern Altstadt in SwissDiv3 and Peter serves on the board of directors for SC Bern. He is a supporter of his hometown football club, BSC Young Boys.

Growing up in Switzerland, Josi played with the local SC Bern from 2006 to 2010. He made his debut with the National League in the 2006–07 season but became a mainstay in the lineup during the 2007–08 season. In his first year of draft eligibility, Josi tallied eight points in 35 games while also representing Switzerland at two international tournaments. Leading up to the 2008 NHL Entry Draft, Josi was considered one of the top defencemen in the draft. He was eventually selected by the Nashville Predators in the second round, 38th overall. Following the draft, Josi returned to the Swiss league where he led all Swiss League junior players in points, goals, and assists. He was also one of just four 17-year-olds to play in Switzerland's top division. Despite being sidelined for almost four weeks during the 2009–10 season, Josi accumulated 20 points through 24 games by the end of December 2009. He eventually finished the season ranked second among Swiss blueliners in points per game despite being limited to only 26 contests. During the 2010 NLA playoffs, Josi led all defensemen and tied for fourth overall in goals as SC Bern won the Championship title.

Josi joined the Predators' organization for the 2010–11 season after he signed a three-year entry-level contract on 28 May 2010. He participated in their Rookie and Training Camp before being assigned to their American Hockey League (AHL) affiliate, the Milwaukee Admirals, for the remainder of the season. Although he missed the first seven games of the season, Josi helped the team improve to a 5–0–0–1 record by scoring his first career AHL goal in a 3–2 win over the Lake Erie Monsters in early November. He recorded 14 points in his first 35 AHL games before breaking out and maintaining a 13-game scoring streak from 20 January to 20 February. His point streak was the longest by an Admiral player since Mike Santorelli maintained a 14-game streak in 2008. By 26 February, Josi had collected 12 points in 11 games during February and ranked among the top 15 in AHL rookie scoring. Josi was subsequently a nominee for the Reebok/AHL Rookie of the Month for February, which he lost to Brandon Kozun. As the Admirals qualified for the 2011 Calder Cup playoffs, Josi finished the regular season with six goals and 34 assists for 30 points through 69 games. During the Admirals West Division semifinal matchup against the Texas Stars, Josi recorded an assist in each of his first four postseason games.

Josi once again participated in the Predators training camp before being placed on injured reserve with the expectation he would report to the Admirals once recovered for the 2011–12 season. Once healthy, Josi tallied four points in his first five games before being recalled to the NHL level on 25 November 2011. He subsequently played 12:20 minutes of ice time in his debut the following day against the Detroit Red Wings. He later scored his first career NHL goal on 10 December to lift the team 3–2 over the Anaheim Ducks. Josi played 12:45 minutes of ice time during the game, including time on the power play, and recorded one blocked shot and one hit. After star defenseman and captain Shea Weber suffered an injury, Josi saw his ice time spike to an average of 23:43 for four games during his absence. Once Weber returned, Josi and fellow rookie defenseman Ryan Ellis were put on the second power-play unit and Josi saw his ice time average out to 20 minutes per game. While playing alongside new teammate Hal Gill, Josi began to play more offensively and began tallying points. He maintained a three-game point streak in February after going pointless for 14 games. Within Gill's first nine games with the team, Josi produced two goals, five points, and +7 plus/minus rating. The two were praised by teammate Ryan Suter who said: "We’re [the forwards] not playing as much as we did before we got Hal (Gill). All of our defensemen are really stepping up right now." This was shortlived, however, as Josi missed nine games with an upper-body injury. In his return on 30 March, he played an important role for Nashville's first three goals scored and he recorded a team-high four shots on goal. Josi helped the Predators finish the season with a 4–1–0 record as they qualified for the 2012 playoffs as the fourth seed in the West. Josi made his playoff debut on 11 April in the first game of the opening round of the 2012 playoffs against the Detroit Red Wings. The Predators would defeat the fifth-seeded Red Wings in five games before being defeated in the second round in five games by the third-seeded Phoenix Coyotes. Josi finished his first playoff playing in all 10 games and being held pointless.

Following his rookie season, Josi returned to his youth team, SC Bern, because of the 2012 NHL lockout. He played alongside NHL stars John Tavares and Mark Streit, both of the New York Islanders. When the lockout was resolved in January 2013, Josi returned to the Predators for training camp. He quickly improved on his rookie seasons point totals and set new career-highs in goals, assists, points, and games played. After the Predators lost Ryan Suter, Josi stepped into a bigger role on the ice alongside Shea Weber. While playing alongside Weber, Josi tallied four goals and 10 assists for 14 points through 31 games. He eventually finished the season with five goals and 13 assists for 18 points through all 48 games as the Predators failed to qualify for the playoffs for the first time since 2009.