Thatcher Douglas Demko (born December 8, 1995) is an American professional ice hockey player who is a goaltender for the Vancouver Canucks of the National Hockey League (NHL). Demko was selected by the Canucks in the second round (36th overall) of the 2014 NHL entry draft.

Demko began playing ice hockey in San Diego at the age of 4. In 2010, he moved to Los Angeles to play youth hockey for the LA Junior Kings. In the 2011–12 season, Demko played with the Omaha Lancers of the United States Hockey League (USHL). He joined the U.S. National Development Team during the 2012–13 season, winning silver medal with the team at the 2012 World U-17 Hockey Challenge.

Demko played for the Boston College Eagles of Hockey East from 2013–2016, serving as the primary starting goaltender for all three seasons. During his college career, he earned an impressive 62–26–10 record, with a .928 save percentage, 2.08 goals allowed average and 13 shutouts. At the time of leaving, he held the school's second best career GAA (2.08), second most wins (62), and third most career shutouts (13). With 10 shutouts in his junior season, he set the school's single-season record and came close to the NCAA record, only second behind Greg Gardner's (Niagara) mark of 12 in 1999–2000.

During his freshman season, he earned a spot on the conference All-Rookie team and won the league's statistical goaltending award for lowest GAA (1.35) in conference play. He also helped the Eagles earn their 5th consecutive title in the prestigious Beanpot tournament played between Boston's elite hockey universities. During the postseason, the Eagles reached the Frozen Four but fell to Union in the semi-final.

After the conclusion of his freshman year, Demko was ranked number 1 by the NHL Central Scouting Bureau on their final list of the top draft-eligible North American goaltenders leading into the 2014 NHL entry draft. He would be picked by the Vancouver Canucks, 36th overall in the 2nd round.

In April 2015, during the offseason following his sophomore year, Demko underwent surgery on both hips at New York City's Hospital for Special Surgery. For almost four years, he had dealt with immense pain from tears in his acetabular labrums, a ring of cartilage at the hips.

In his junior season, Demko shone with a staggering 27–8–4 record, with a 1.88 GAA and .935 save percentage. He helped the Eagles once again reach the Frozen Four, but again fell in the semi-final, this time to Quinnipiac. For his efforts, he was named the recipient of the Mike Richter Award, given to the most outstanding goaltender in NCAA men's ice hockey, and was also a top 3 finalist for the Hobey Baker Award, given to the best overall player in the NCAA. He also earned a number of other accolades, making the AHCA All-American Second Team, the Hockey East First All-Star team, and finally was named Co-Player of the Year by Hockey East, alongside UMass Lowell's goaltender Kevin Boyle

Forgoing his senior year at Boston College, Demko signed a three-year entry-level contract with the Canucks on April 20, 2016.