| Date: | 26 July–1 August 2021 |
| Edition: | 13th |
| Surface: | Clay |
| Location: | Versmold, Germany |
| Category: | ITF Women's World Tennis Tour |
| Prize Money: | $60,000 |
| Champs: |  Elina Avanesyan |
| Champd: |  Anna Danilina /  Valeriya Strakhova |
| Before Year: | 2019 |
The 2021 Reinert Open was a professional women's tennis tournament played on outdoor clay courts. It was the thirteenth edition of the tournament which was part of the 2021 ITF Women's World Tennis Tour. It took place in Versmold, Germany between 26 July and 1 August 2021.[1]
| Country | Player | Rank1 | Seed | |
|---|---|---|---|---|
| Tamara Korpatsch | 162 | 1 | ||
 Spain | Lara Arruabarrena | 192 | 2 | |
 Austria | Julia Grabher | 201 | 3 | |
| Daniela Seguel | 224 | 4 | ||
| Katharina Gerlach | 225 | 5 | ||
| Alycia Parks | 240 | 6 | ||
| Richèl Hogenkamp | 241 | 7 | ||
 Belgium | Marie Benoît | 242 | 8 |
The following players received wildcards into the singles main draw:
The following players received entry using protected rankings:
The following players received entry from the qualifying draw:
Federica Arcidiacono Jéssica Bouzas Maneiro Cristiana Ferrando
Elizabeth Halbauer Ekaterina MakarovaThe following player received entry as a lucky loser:
See main article: 2021 Reinert Open – Singles.
Elina Avanesyan def. Federica Di Sarra, 6–7(4–7), 6–2, 6–2See main article: 2021 Reinert Open – Doubles.
Anna Danilina / Valeriya Strakhova def. 
Mirjam Björklund / 
Jaimee Fourlis, 4–6, 7–5, [10–4]