Marcel Theodor Keßen (alternative spelling Kessen; born 2 January 1997) is a German professional basketball player.

[1] In January 2021, he returned to Phoenix Hagen after a 3-year absence.

[2] In June 2022, under the lead of coach Chris Harris, Keßen became Hagen's new team captain.

In the 2022–23 season, Keßen advanced to become Hagen's second-best scorer with an average of 14.3 points.

Out of 29 games played, he was in the starting lineup 27 times and had an excellent three-point percentage of 43 percent.