Douglas Robert Gilmour (born June 25, 1963) is a Canadian former professional ice hockey player. He played 20 seasons in the National Hockey League (NHL) for seven different teams. Gilmour was a seventh round selection, 134th overall, of the St. Louis Blues at the 1982 NHL Entry Draft and recorded 1,414 points in 1,474 games in the NHL between 1983 and 2003. A two-time All-Star, he was a member of Calgary's 1989 Stanley Cup championship team and won the Frank J. Selke Trophy as the NHL's best defensive forward in 1992–93. Internationally, he represented Canada three times during his career and was a member of the nation's 1987 Canada Cup championship team.

Gilmour was nicknamed "Killer" by a Blues teammate possibly due to his having the same last name as serial killer Gary Gilmore (though others have attributed it to his physical style of play despite his small stature). He played three seasons of junior hockey for the Cornwall Royals where he was a member of their Memorial Cup championship team in 1981. In 1982–83, Gilmour was named the most outstanding player in the Ontario Hockey League (OHL) after he scored 177 points, one of the highest totals in league history. Gilmour returned to the OHL following his playing career as he joined the Kingston Frontenacs as head coach in 2008 and was promoted to general manager in 2011. Gilmour was inducted into the Hockey Hall of Fame and the Ontario Sports Hall of Fame in 2011 and his uniform number 93 is retired by the Toronto Maple Leafs.

Doug Gilmour was born June 25, 1963, in Kingston, Ontario. He is the younger son of Don and Dolly Gilmour, and has an elder brother, David. Don was a correctional officer who worked at the Kingston Penitentiary for over three decades. He also coached youth baseball and hockey teams in the city. As a youth, Doug looked up to David, who was a professional hockey player drafted by the Vancouver Canucks but never played in the National Hockey League (NHL). The younger Gilmour played in the 1976 Quebec International Pee-Wee Hockey Tournament with a minor ice hockey team from Kingston.

Gilmour's small size – he stood five feet, nine inches tall and weighed 140 pounds in junior hockey – resulted in his being cut from several teams throughout his minor hockey career. Originally a defenceman, Gilmour began his 16-year-old season (1979–80) in Junior B with his hometown Kingston Voyageurs. Given only three minutes of ice time per game, he asked the team for his release so that he could return to Major Midget hockey where he would get more ice time. Instead, he was offered a spot with the Junior A Belleville Bulls, with whom he began as a defenceman but shifted to left wing during the playoffs due to injuries.

The Cornwall Royals of the major junior Quebec Major Junior Hockey League (QMJHL) drafted Gilmour from Belleville, and he joined the team for the 1980–81 season. The Royals were the defending Memorial Cup champions, and Gilmour was not expected to play a significant role with the team. The Royals started him off as an offensive defenceman, but moved him to forward permanently. As national champions, the Royals represented Canada at the 1981 World Junior Ice Hockey Championships. Gilmour appeared in all five tournament games, though he scored no points, as the team struggled to a seventh-place finish in the eight team tournament. In the QMJHL, Gilmour's season was interrupted by a broken collarbone. He finished the year with 35 points in 51 games. The Royals won the QMJHL championship and earned a berth in the 1981 Memorial Cup. Gilmour recorded seven points in five games at the tournament. Cornwall faced the Ontario Hockey League (OHL)'s Kitchener Rangers in the championship game. Cornwall won 5–2 to repeat as national champions; Gilmour scored the winning goal midway through the second period.

Though eligible for the 1981 NHL Entry Draft, Gilmour went unselected and returned to Cornwall, who had shifted to the OHL for the 1981–82 season. He played a more significant role with the Royals and led the team offensively; Gilmour's 119 points in 67 games was sixth best in the league. NHL teams continued to dismiss Gilmour due to his size, but the St. Louis Blues gambled on him in the 1982 NHL Entry Draft by selecting him with their seventh round pick, 134th overall. The Blues returned him to Cornwall for the 1982–83 season where he led the OHL in goals (70), assists (107) and points (177). Gilmour won the Eddie Powers Memorial Trophy as the leading scorer, was named a league all-star, and was named recipient of the Red Tilson Trophy as the OHL's most outstanding player. His season total of 177 points is the third highest in OHL history, behind Bobby Smith (192) and Wayne Gretzky (182). Gilmour had a 55-game point streak that lasted from October 19, 1982, until February 27, 1983, and which remains an OHL record.

Despite his performance in Cornwall, the Blues did not make signing Gilmour a priority. Unsure if a contract offer would materialize, Gilmour made plans to play in Düsseldorf, West Germany, and had already traveled to Europe when the Blues finally offered him a deal in mid-August 1983. St. Louis coach Jacques Demers believed Gilmour had the potential to be a defensive specialist at forward. He began the 1983–84 season in St. Louis and made his NHL debut on October 4, 1983, against the Pittsburgh Penguins. Gilmour scored his first goal on November 1, in his 12th game, against Eddie Mio of the Detroit Red Wings. He finished the season with 25 goals and 53 points. Teammate Brian Sutter began calling Gilmour "Charlie", after Charles Manson, in reference to both his "mean" style of play and an apparent resemblance to the serial killer; it morphed into "Killer", a nickname Gilmour retained throughout his career.

Gilmour's offensive performances were consistent in his following two seasons. He recorded 57 points in 1984–85 and 53 points in 1985–86. Defensively, Demers matched Gilmour up at centre against the opposition's best players and he played an agitator role. Over time, he gained confidence in his ability to both defend against the opposition and play an offensive role. Gilmour established a role as a top offensive scorer for the Blues in the 1986 Stanley Cup playoffs as he recorded 21 points in 19 games. He tied with teammate Bernie Federko for the league lead in playoff scoring, despite the fact that the Blues failed to reach the Stanley Cup Finals. The Blues were eliminated in the Campbell Conference Final by the Calgary Flames. His offensive breakout continuing into the 1986–87 season, Gilmour led the Blues and finished fifth overall in NHL scoring with 105 points; his 42 goals was the highest single-season total of his career. His performance in the NHL season earned Gilmour an invitation to join Team Canada at the 1987 Canada Cup. He had two goals in the tournament as Canada won the championship.