| Kristoffer Tønnessen | |
| Birth Date: | 1 October 1997 |
| Position: | defender |
| Currentclub: | Lillestrøm |
| Clubnumber: | 19 |
| Youthclubs1: | Jerv |
| Years1: | 2013–2019 |
| Clubs1: | Jerv |
| Caps1: | 108 |
| Goals1: | 2 |
| Years2: | 2019–2022 |
| Clubs2: | Start |
| Caps2: | 93 |
| Goals2: | 7 |
| Years3: | 2023– |
| Clubs3: | Lillestrøm |
| Caps3: | 20 |
| Goals3: | 3 |
| Nationalyears1: | 2017 |
| Nationalteam1: | Norway U21 |
| Nationalcaps1: | 2 |
| Nationalgoals1: | 0 |
| Pcupdate: | 4 December 2023 |
Kristoffer Tønnessen (born 1 October 1997) is a Norwegian football defender who plays for Lillestrøm.
He made his league debut for Jerv in the 2013 3. divisjon, and took part in successive promotions to the 2016 1. divisjon. At the end of the season, Jerv was only minutes away from yet another promotion, but ultimately lost the decisive playoff match. The next year, Tønnessen made his debut for Norway U21. In the summer of 2019 he went to Start, for whom he made his first-tier debut in June 2020 against Strømsgodset. Tønnessen made 100 Start appearances across all competitions. Ahead of the 2023 season he went to Lillestrøm SK, featuring on their losing team in the 2022–23 Norwegian Football Cup final.