Matthieu Ladagnous (born 12 December 1984) is a French former road and track racing cyclist, who competed as a professional from 2006 to 2023, spending his entire career with UCI WorldTeam Française des Jeux.^[4]

Riding entirely for the Française des Jeux team and its succeeding iterations since his début in 2006, Ladagnous has taken eleven victories during his professional career, including victories in the 2007 Four Days of Dunkirk and 2009 La Tropicale Amissa Bongo Ondimbo stage races.

Born in Pau, Ladagnous became junior world champion at the madison in Melbourne, Australia in 2002 with his partner Tom Thiblier. In 2003 he won the French national title at the points race for the under-23 level. He also won a bronze medal at the individual sprint (under-23) and a silver medal at the madison with Fabien Patanchon in the elite class. Later that year he and Patanchon became European champions at the under-23 track cycling championships. A year later he won the bronze medal at the scratch in the 2003 under-23 championships. He improved his bronze national individual pursuit manager into a gold, while his points race gold was changed in a silver in 2004. In the elite class he won the madison gold, again alongside Patanchon.

In 2005 he first continued as a track cyclist and added another national under-23 silver to his palmarès at the individual pursuit. A silver medal in the elite class was added at the madison where he teamed up with Patanchon again. At the team pursuit he, Anthony Langella, Fabien Sanchez and Mickaël Mallie won the gold medal and became national elite champions. At the 2005 European championships in Fiorenzuola d'Arda he won a silver medal at the points race. In 2005 he also made his first road cycling appearance. He immediately won the prologue in the Mainfranken-Tour (under-23) and the overall classification. He decided to focus mainly at the road for the 2006 season, but won another team pursuit gold with Mickaël Delage, Jonathan Mouchel, Mikaël Preau and Sylvain Blanquefort. He booked his first road race win in 2006, when he won the fifth stage of the Tour Méditerranéen. The following year he won the fifth stage and the general classification of the Four Days of Dunkirk.

He was named in the start list for the 2017 Giro d'Italia.^[5]

In January 2023, entering his eighteenth season as a professional – all with Groupama–FDJ and its preceding iterations – Ladagnous announced that he would retire from the sport at the end of the year.^[6]

He is the brother of French rugby union international Caroline Ladagnous.^[7]