Thomas De Gendt (born 6 November 1986) is a Belgian former road racing cyclist, who competed as a professional from 2009 to 2024.

The winner of the mountains classification at the 2018 Vuelta a España, De Gendt has also finished on the podium at the 2012 Giro d'Italia, where he was third overall.

In his first season at UCI Professional Continental level with Topsport Vlaanderen–Mercator in 2009, Sint-Niklaas-born De Gendt won the Internationale Wielertrofee Jong Maar Moedig one-day race,[8] a stage of the Tour de Wallonie,[9] and the mountains and sprints classifications at the Tour of Britain.

[16][17] He took one other victory during the season – a stage at the Circuit de Lorraine[18] – as he extended his contract with the team, until the end of 2013.

[20] In the Giro d'Italia, he won the penultimate stage at the Stelvio Pass with a solo breakaway which brought him to fourth in the general classification.

[33] In his first start of the 2017 season, De Gendt won the mountains classification at the Tour Down Under, taking the jersey from Richie Porte on the final day of the race.

[40] He added to his string of long breakaway victories by winning the second stage of the Tour de Romandie in solo fashion.

[54] At the 2022 Giro d'Italia, De Gendt took his first stage victory at the race for a decade,[55] winning a hilly stage in and around Naples; he was part of a four-rider move that broke away from a larger breakaway group with approximately 40 kilometres (25 miles) remaining, and was assisted by his teammate Harm Vanhoucke in the final sprint to the line.