2021 BGL Luxembourg Open – Singles

Jeļena Ostapenko was the defending champion, having won the previous edition in 2019, but lost to Clara Tauson in the final, 3–6, 6–4, 4–6.

Seeds
• # Belinda Bencic (quarterfinals)

• # 🇧🇪 Elise Mertens (quarterfinals)

• # Jeļena Ostapenko (final)

• # 🇷🇺 Ekaterina Alexandrova (second round)

• # 🇨🇿 Markéta Vondroušová (semifinals)

• # 🇨🇳 Zhang Shuai (first round)

• # 🇷🇺 Liudmila Samsonova (semifinals)

• # 🇫🇷 Alizé Cornet (quarterfinals)

Seeds
• # 🇦🇺 Astra Sharma (moved to main draw)

• # 🇷🇺 Vitalia Diatchenko (first round, retired)

• # 🇩🇪 Jule Niemeier (qualified)

• # 🇩🇪 Tamara Korpatsch (first round)

• # 🇪🇸 Cristina Bucșa (qualifying competition)

• # 🇷🇺 Anastasia Gasanova (qualifying competition)

• # 🇷🇺 Natalia Vikhlyantseva (first round)

• # 🇺🇦 Lesia Tsurenko (qualified)

• # 🇪🇸 Lara Arruabarrena (first round)

• # Indy de Vroome (first round)

• # Jana Fett (qualified)

• # 🇧🇬 Isabella Shinikova (first round)

Qualifiers
• # 🇷🇺 Anastasia Zakharova

• # 🇷🇺 Ekaterina Makarova

• # 🇩🇪 Jule Niemeier

• # Arianne Hartono

• # 🇺🇦 Lesia Tsurenko

• # Jana Fett