Jamieson Oleksiak (born December 21, 1992) is a Canadian professional ice hockey player who is a defenceman for the Seattle Kraken of the National Hockey League (NHL). Nicknamed the "Big Rig", Oleksiak was selected 14th overall in the first round of the 2011 NHL entry draft by the Dallas Stars, the highest draft choice in Northeastern University's history.

Oleksiak attended Northeastern University for one year and had 13 points on 4 goals and 9 assists and team-best +13 plus/minus. After his freshman season with the Northeastern Huskies, Oleksiak decided to return to the Canadian Hockey League for further development, and on July 25, 2011, the Saginaw Spirit announced that they had signed Oleksiak to an Ontario Hockey League contract, and on October 6, 2011, it was announced that Oleksiak had signed a three-year entry-level contract with the National Hockey League's Dallas Stars. With the Spirit out of contention during the 2011–12 season, Oleksiak was traded to the title-contending Niagara IceDogs on January 10, 2012.

Following the 2011–12 season, Oleksiak turned professional and was assigned to the Stars' American Hockey League affiliate, the Texas Stars, to begin the 2012–13 season. He tallied his first professional point on October 14 in a win over the Charlotte Checkers. He later scored his first professional goal, the game-winner, on October 24. Through the first 13 games of the 2012–13 season, Oleksiak tallied one goal and four assists to tie for the team lead in scoring among defensemen. He continued to produce as the season continued and quickly accumulated two goals and 10 assists through the next 25 games. As a result of his outstanding play, Oleksiak earned his first NHL callup on January 15, 2013. The callup was short-lived however as he was shortly thereafter reassigned to the AHL. Upon returning to the AHL, Oleksiak continued to shine offensively and was named to the 2012 AHL All-Star Game in Providence, Rhode Island. At the time of the selection, he led the Stars and ranked third amongst all rookies in assists with 20. He was also recognized as the AHL's Rookie for the Month of January.

Shortly after these selections, Oleksiak was recalled to the NHL level on January 31, 2013. He subsequently made his NHL debut on February 1 in a 4–3 win over the Phoenix Coyotes. Upon making his NHL debut listed at 6-foot-7, Oleksiak became the tallest player in Dallas Stars history to play for the team. Over the next five games, he averaged nearly 16 minutes of ice time but remained pointless. He eventually tallied his first NHL assist on February 13 in a game against the Calgary Flames but was reassigned to the AHL the following day. Oleksiak played five games for the Texas Stars before being recalled to the NHL level again on February 24. Despite playing just five games since February 1, he still ranked first among team defensemen in scoring and plus/minus (+20). Oleksiak played a total of 16 games for the Dallas Stars during the 2012–13 season, accumulating two assists, 14 penalty minutes and 11 shots. He struggled near the end of his time with the Dallas Stars and had two assists and a minus-5 rating. Oleksiak finished his first AHL season with six goals and 27 assists for 33 points through 59 games. He also participated in the 2013 Calder Cup playoffs where he tallied one assist through nine games. During the 2013 offseason, Oleksiak changed his Dallas Stars jersey number from 43 to 5.

Oleksiak participated in four preseason games with the Dallas Stars before being returned to the AHL for the 2013–14 season. He began the season strong, leading all Texas defensemen with three goals through the first 22 games of the season. Following an injury to defenseman Stephane Robidas, Oleksiak earned his first NHL recall of the season on November 30. He played in seven games for the Stars, collecting five shots and two penalty minutes, before being reassigned to the AHL on December 18. Upon returning to the AHL, Oleksiak helped the Texas Stars win the 2014 Calder Cup playoffs.

In the final year of his entry-level contract, Oleksiak dipped in production at the AHL level but tallied eight points through 36 games with the Dallas Stars in the NHL. For the first time, Oleksiak was named to the Dallas Stars' opening night roster for the 2014–15 season. He was one of six defencemen the Stars planned on relying on throughout the season. However, as injuries befell the roster, the Stars recalled numerous defencemen from their AHL affiliate through the season. Oleksiak scored his first career NHL goal on October 28, in the first period of an eventual 4–3 overtime loss to the St. Louis Blues. However, he struggled to continue to produce and was reassigned to the Texas Stars on December 11, after accumulating four points through 21 games. He recorded two shots on goal in one game with the Texas Stars before being recalled to the NHL level on December 13. He played one more game for the Dallas Stars before returning to the AHL on December 23. Upon returning to the AHL, Oleksiak recorded two assists through two games before returning to the NHL level on December 29. Throughout the months of January and February, Oleksiak and Jyrki Jokipakka split their time between the NHL and AHL. Oleksiak accumulated four more points with the Stars before returning to the AHL level in mid-January while the Dallas Stars were on break. Once the NHL resumed play, Oleksiak returned to the NHL level on January 26. He finished the NHL season with eight points through 36 games. On July 9, 2015, Oleksiak signed a one-year contract extension to remain with the Dallas Stars.

Following the signing of the contract extension, Oleksiak saw limited playing time during the 2015–16 season and was consistently a healthy scratch. He played in four of the Dallas Stars' first 20 games to begin the season. As he was waiver eligible, the Stars were reluctant to assign him to the AHL level. As the season continued, he recorded two assists and 37 hits through 11 games before being assigned to the Texas Stars on a conditioning assignment. At the time of the assignment, he had played one game since December 12. He skated in eight games for Texas during the assignment, recording one assist, before being recalled to the NHL level on February 1, 2016. Due to injuries to three of the Stars' top six defensemen, head coach Lindy Ruff opted to give Oleksiak, Kris Russell, Alex Goligoski, Johnny Oduya, and Patrik Nemeth longer minutes during games throughout March. However, he saw very little games during March and ended the season with two points in 19 games. Despite his poor performance, the Stars signed Oleksiak to another one-year contract on July 12, 2016.

Following the signing of the contract extension, Oleksiak experienced his first full season in the NHL with Dallas during the 2016–17 season. During the offseason, the Stars parted ways with veteran defencemen Alex Goligoski, Jason Demers, and Kris Russell, leaving an opening for Oleksiak to earn more playing time. He quickly made use of this opportunity and impressed head coach Lindy Ruff while paired with Esa Lindell in mid-October. However, he became a healthy scratch once again and missed nine games since October 20 before rejoining the lineup on November 10 as the Stars experienced a three-game losing streak. As he slowly became a mainstay in the lineup, Oleksiak began to bounce back from the previous season. He tallied five goals and one assist through 20 games before suffering a hand injury during a game against the Anaheim Ducks on January 13, 2017. He subsequently missed 13 games before returning on February 11 to play alongside Stephen Johns in a 5–2 win against the Carolina Hurricanes. Oleksiak finished the regular season with a career-high five goals and two assists for seven points through 41 games. On August 4, 2017, the Stars re-signed Oleksiak to a one-year, $964,688 contract.