| Date: | 11–17 October 2021 |
| Edition: | 11th |
| Surface: | Hard |
| Location: | Rancho Santa Fe, California, United States |
| Category: | ITF Women's World Tennis Tour |
| Prize Money: | $60,000 |
| Champs: |  Rebecca Peterson |
| Champd: |  Katarzyna Kawa /  Tereza Mihalíková |
The 2021 Rancho Santa Fe Open was a professional women's tennis tournament played on outdoor hard courts. It was the eleventh edition of the tournament which was part of the 2021 ITF Women's World Tennis Tour. It took place in Rancho Santa Fe, California, United States between 11 and 17 October 2021.[1]
| Country | Player | Rank1 | Seed | |
|---|---|---|---|---|
| Sweden | Rebecca Peterson | 76 | 1 | |
 France | Fiona Ferro | 83 | 2 | |
| Madison Brengle | 88 | 3 | ||
 Kazakhstan | Zarina Diyas | 108 | 4 | |
 Japan | Misaki Doi | 109 | 5 | |
| Slovakia | Kristína Kučová | 112 | 6 | |
 Mexico | Renata Zarazúa | 118 | 7 | |
| Polona Hercog | 123 | 8 |
The following players received wildcards into the singles main draw:
The following player received entry using a protected ranking:
The following player received entry as a junior exempt:
The following player received entry as a special exempt:
The following players received entry from the qualifying draw:
Ellie Douglas Haley Giavara Dalayna Hewitt Elvina Kalieva Ashlyn Krueger Maegan Manasse Tereza Mihalíková Marine PartaudSee main article: 2021 Rancho Santa Fe Open – Singles.
Rebecca Peterson def. Elvina Kalieva, 6–4, 6–0.See main article: 2021 Rancho Santa Fe Open – Doubles.
Katarzyna Kawa / Tereza Mihalíková def. Liang En-shuo / 
Rebecca Marino, 6–3, 4–6, [10–6].