|Full name||Nikolaos Giantsopoulos|
|Date of birth||June 24, 1994|
|Place of birth||Markham, Ontario, Canada|
|Height||1.82 m (6 ft 0 in)|
|* Senior club appearances and goals counted for the domestic league only and correct as of October 5, 2019|
Giantsopoulos played youth soccer with Pickering SC.
In March 2016, Giantsopoulos joined Devonport City in the NPL Tasmania, the second tier of football in Australia. He started all 21 matches for Devonport in the 2016 season, helping to lead the team to a league championship and was named to the NPL Team of the Year. In the 90th minute of the Round of 16 match in the FFA Cup against Bentleigh Greens with the score at 0-0, he suffered a shoulder injury and was forced to leave the game, which Devonport ultimately lost 1-0, after extra time . As a result of the injury, he also missed the Semi-Finals and Finals of the NPL Tasmania Playoff Series, where Devonport ultimately lost in the Finals,  as well as the NPL Finals Series for the champions of each of the regional leagues. 
Giantsopoulos would return to the Tasmania regional division, signing with NPL Tasmania club Lauceston City for the 2018 season. He would be named vice captain of the club, and would start all 21 matches in 2018. On August 18, in a match against South Hobart, as a penalty shot was about to be taken, Giantsopoulos ran up and kicked the ball away before it could be taken. He was yellow carded, but his antics proved to be effective, as the ensuing penalty shot was missed. The incident became a viral video around the world. He was named to the NPL Tasmania Team of the Year at the end of the season. 
Giantsopoulos returned to Canada and signed with Cavalry FC of the Canadian Premier League on January 23, 2019. He served as the backup goalkeeper behind Marco Carducci. He made his debut on May 16 in a Canadian Championship match against Pacific FC. After the season, he re-signed with the club for an additional year.
- As of 18 October 2019
|Devonport City||2016||NPL Tasmania||21||0||1||0||5||0||—||27||0|
|Broadmeadow Magic||2017||NPL Northern NSW||20||0||1||0||5||0||—||26||0|
|Launceston City||2018||NPL Tasmania||21||0||—||3||0||—||24||0|
|Cavalry FC||2019||Canadian Premier League||5||0||0||0||4||0||—||9||0|
- NPL Tasmania Champions: 2016
- NPL Tasmania Playoff Runner-Up: 2016
- Milan Lakoseljac Cup Champions: 2016
- Canadian Premier League (Regular season):
- Canadian Premier League Finals
- Runners-up: 2019
- Wildrose Cup: 2019
- "Three area soccer teams in Ontario Cup finals". durhamregion.com. 4 September 2008. Retrieved 2 July 2019.
- "Niko Giantsopoulos Signs Professional Soccer Contract in Australia". March 15, 2016.
- "Devonport City 2016 stats". SportsTG.
- Shaun McManus (26 August 2016). "Devonport Strikers dominate team of the year". themercury.com.au. Retrieved 2 July 2019.
- Camron Slessor (31 August 2016). "Devonport Strikers keeper in high spirits following painful FFA Cup injury". theadvocate.com.au. Retrieved 2 July 2019.
- Brad Cole (1 September 2016). "Weary Strikers Ready". theadvocate.com.au. Retrieved 2 July 2019.
- Andrew Cooling (15 September 2016). "Devonport head west for Perth challenge". nationalpremierleagues.com.au. Retrieved 2 July 2019.
- Camron Slessor (16 November 2016). "Devonport Strikers goalkeeper Niko Giantsopoulos makes move to Broadmeadow Magic". theadvocate.com.au. Retrieved 2 July 2019.
- Andrew Mathieson (July 13, 2018). "Launceston City goalkeeper Niko Giantsopoulos has big goals for his adopted NPL club". The Examiner.
- "Launceston City 2018 stats". SportsTG.
- Football Tasmania (August 18, 2018). "Giant Sized Mind Games". Facebook.
- "2018 NPL TAS TEAM OF THE YEAR". September 12, 2018.
- "Four More Horsemen Saddle Up to Ride with Cavalry FC". January 23, 2019.
- "Cavalry FC open the 2019 Canadian Championship with 0:2 away win over Pacific FC". May 16, 2019.
- "Cavalry locks up three more key pieces". December 5, 2019.
- Includes other competitive competitions such as NPL Playoff Finals and CPL Playoffs.
- Includes FFA Cup, Milan Lakoseljac Cup and Canadian Championship
- John Jacques (12 September 2019). "Cavalry FC Wins First Silverware With Wildrose Cup". northerntribune.ca. Retrieved 12 September 2019.
- Niko Giantsopoulos at Soccerway