Guillaume Jannez (born 19 February 1989) is a French footballer who plays as a centre-back for Championnat National club Concarneau.

[4] He began his senior career with FC Quimperlé in 2006, and in 2007 transferred to Concarneau who were at the Championnat National 2 at the age of 18.

[2] At the age of 20, he shifted from midfielder to centre-back and was named captain of the club by his then manager Nicolas Cloarec.

[5] He captained Concarneau as they won the 2022–23 Championnat National and earned promotion to the Ligue 2 for the first time in their history.

[7] At the age of 34, Jannez made his professional debut with Concarneau, a 0–0 Ligue 2 tie with Bastia on 5 August 2023.