2019 Libéma Open – Men's singles

Adrian Mannarino defeated Jordan Thompson in the final, 7–6(9–7), 6–3 to win the men's singles tennis title at the 2019 Rosmalen Grass Court Championships. It was Mannarino's maiden ATP Tour singles title in his seventh final. Thompson was also contesting for his maiden title.

Richard Gasquet was the defending champion, but lost to Thompson in the semifinals.

Seeds
The top four seeds receive a bye into the second round. • # Stefanos Tsitsipas (second round)

• # Borna Ćorić (semifinals)

• # 🇦🇺 Alex de Minaur (quarterfinals)

• # 🇪🇸 Fernando Verdasco (second round)

• # 🇧🇪 David Goffin (quarterfinals)

• # 🇺🇸 Frances Tiafoe (second round)

• # Cristian Garín (quarterfinals)

• # 🇫🇷 Richard Gasquet (semifinals)

Seeds
• # 🇺🇸 Bradley Klahn (first round)

• # 🇮🇹 Thomas Fabbiano (qualifying competition, lucky loser)

• # Jason Jung (first round)

• # 🇦🇺 Alex Bolt (first round)

• # 🇺🇸 Tommy Paul (qualified)

• # 🇪🇸 Alejandro Davidovich Fokina (qualified)

• # 🇸🇰 Lukáš Lacko (first round)

• # 🇮🇹 Salvatore Caruso (qualified)

Qualifiers
• # 🇪🇸 Alejandro Davidovich Fokina

• # 🇮🇹 Jannik Sinner

• # 🇮🇹 Salvatore Caruso

• # 🇺🇸 Tommy Paul

Lucky loser

 * 1) 🇮🇹 Thomas Fabbiano