| Doubles | |
|---|---|
| 2021 WTA Finals | |
| Champions | |
| Runners-up | |
| Score | 6–3, 6–4 | 
| Draw | 8 (round robin) | 
Barbora Krejčíková and Kateřina Siniaková defeated Hsieh Su-wei and Elise Mertens in the final, 6–3, 6–4 to win the doubles tennis title at the 2021 WTA Finals.
Tímea Babos and Kristina Mladenovic were the two-time reigning champions, but failed to qualify this year.[1]
Krejčíková and Siniaková clinched the year-end no. 1 as a team with their win against Sharon Fichman and Giuliana Olmos in their first round-robin match, and Siniaková secured the individual year-end no. 1 ranking by winning the title. Hsieh was also in contention for the top ranking.[2]
Seeds
 Barbora Krejčíková / 
 Kateřina Siniaková (champions)
 Shuko Aoyama / 
 Ena Shibahara (semifinals)
 Hsieh Su-wei / 
 Elise Mertens (final)
 Nicole Melichar-Martinez / 
 Demi Schuurs (semifinals)
 Samantha Stosur / 
 Zhang Shuai (round robin)
 Alexa Guarachi / 
 Desirae Krawczyk (round robin)
 Darija Jurak / 
 Andreja Klepač (round robin)
 Sharon Fichman / 
 Giuliana Olmos (round robin)
Alternates
 Nadiia Kichenok / 
 Raluca Olaru (Did not play)
 Marie Bouzková / 
 Lucie Hradecká (Did not play)
Draw
Key
- Q = Qualifier
 - WC = Wild card
 - LL = Lucky loser
 - Alt = Alternate
 - SE = Special exempt
 - PR = Protected ranking
 - ITF = ITF entry
 - JE = Junior exempt
 - w/o = Walkover
 - r = Retired
 - d = Defaulted
 - SR = Special ranking
 
Finals
| Semifinals | Final | ||||||||||||
| 1 | 3 | 6 | [10] | ||||||||||
| 4 | 6 | 3 | [6] | ||||||||||
| 1 | 6 | 6 | |||||||||||
| 3 | 3 | 4 | |||||||||||
| 2 | 2 | 2 | |||||||||||
| 3 | 6 | 6 | |||||||||||
Group El Tajín
| RR W–L | Set W–L | Game W–L | Standings | ||||||
| 1 | 6–3, 6–1 | 5–7, 7–6(7–3), [10–7] | 6–4, 6–1 | 3–0 | 6–1 (86%) | 37–22 (63%) | 1 | ||
| 3 | 3–6, 1–6 | 7–6(7–3), 6–2 | 6–4, 7–6(7–3) | 2–1 | 4–2 (67%) | 30–30 (50%) | 2 | ||
| 6 | 7–5, 6–7(3–7), [7–10] | 6–7(3–7), 2–6 | 0–6, 6–3, [11–9] | 1–2 | 3–5 (38%) | 28–35 (44%) | 3 | ||
| 8 | 4–6, 1–6 | 4–6, 6–7(3–7) | 6–0, 3–6, [9–11] | 0–3 | 1–6 (14%) | 24–32 (43%) | 4 | 
Group Tenochtitlán
| RR W–L | Set W–L | Game W–L | Standings | ||||||
| 2 | 6–4, 7–6(7–5) | 6–4, 3–6, [7–10] | 6–0, 6–4 | 2–1 | 5–2 (71%) | 34–25 (58%) | 1 | ||
| 4 | 4–6, 6–7(5–7) | 6–2, 6–2 | 6–4, 3–6, [10–2] | 2–1 | 4–3 (57%) | 32–27 (54%) | 2 | ||
| 5 | 4–6, 6–3, [10–7] | 2–6, 2–6 | 7–6(12–10), 6–7(4–7), [5–10] | 1–2 | 3–5 (38%) | 28–35 (44%) | 4 | ||
| 7 | 0–6, 4–6 | 4–6, 6–3, [2–10] | 6–7(10–12), 7–6(7–4), [10–5] | 1–2 | 3–5 (38%) | 28–35 (44%) | 3 | 
Standings are determined by: 1. number of wins; 2. number of matches; 3. in two-player ties, head-to-head records; 4. in three-player ties, (a) percentage of sets won (head-to-head records if two players remain tied), then (b) percentage of games won (head-to-head records if two players remain tied), then (c) WTA rankings.
References
- ↑ "'There was no one out there who could beat us' - Babos, Mladenovic defend WTA Finals title with defeat of Hsieh, Strycova". Women's Tennis Association. 3 November 2019. Archived from the original on 2019-11-12. Retrieved 2021-11-09.
 - ↑ "Krejcikova, Siniakova sweep past Hsieh, Mertens to win WTA Finals doubles title". Women's Tennis Association. 18 November 2021. Archived from the original on 2021-11-18. Retrieved 2021-11-18.