Medvedev, the former world number one, hardly counts the French Open as his favorite tournament.
It is the seventh time in ten starts that the Russian has been eliminated in the first round.
After three and a half hours of play in 32-degree heat, Adam Walton emerged victorious 6–2, 1–6, 6–1, 1–6, 6–4.
This is the first time the 27-year-old Walton has beaten a top-10 player.
This makes sixth-seeded Medvedev the highest-seeded men's singles player to be eliminated so far. Seventh-seeded Taylor Fritz has also been eliminated from the year's second Grand Slam tournament.
