The 2021 Cincinnati Reds season was the 152nd season for the franchise in Major League Baseball, and their 19th at Great American Ball Park in Cincinnati.

The first to be broadcast on the rebranded Bally Sports Ohio, it would also be memorable as the first for a new PBP television broadcaster for the Reds, John Sadak. This came after previous play-by-play announcer Thom Brennaman was fired during the previous season for his controversial homophobic remarks on the air during a game.

The Reds stayed in contention for most of the season after making the playoffs the previous year. However, a late September slump ultimately eliminated them from the postseason for the 7th time in the last 8 seasons and the 7th straight full season. Despite this, they still finished with a winning record at 83–79 to finish with back to back winning records for the first time since 2012 and 2013.

Offseason Trades December 7, 2020: Traded reliever Raisel Iglesias to the Los Angeles Angels for reliever Noe Ramirez and a player to be named later, subsequently announced as Leo Rivas. Signings February 8, 2021: Signed reliever Sean Doolittle a one-year, $1.5 million contract.

Regular season

Standings National League Central

National League Wildcard

Record vs. opponents

Game log

|-style="background:#fbb;" | 1 || April 1 || Cardinals || 6–11 || Gallegos (1–0) || Castillo (0–1) || — || 12,695 || 0–1 || L1 |-style="background:#bfb;" | 2 || April 3 || Cardinals || 9–6 || Mahle (1–0) || Wainwright (0–1) || — || 12,213 || 1–1 || W1 |-style="background:#bfb;" | 3 || April 4 || Cardinals || 12–1 || Hoffman (1–0) || Martínez (0–1) || — || 11,629 || 2–1 || W2 |-style="background:#bfb;" | 4 || April 5 || Pirates || 5–3 || Doolittle (1–0) || Howard (1–1) || Garrett (1) || 9,097 || 3–1 || W3 |-style="background:#bfb;" | 5 || April 6 || Pirates || 14–1 || Miley (1–0) || Cahill (0–1) || — || 11,093 || 4–1 || W4 |-style="background:#bfb;" | 6 || April 7 || Pirates || 11–4 || Castillo (1–1) || Kuhl (0–1) || — || 11,463 || 5–1 || W5 |-style="background:#bfb;" | 7 || April 9 || @ Diamondbacks || 6–5 || Pérez (1–0) || Young (0–2) || Garrett (2) || 19,385 || 6–1 || W6 |-style="background:#fbb;" | 8 || April 10 || @ Diamondbacks || 3–8 || Smith (1–0) || Hoffman (1–1) || — || 13,208 || 6–2 || L1 |-style="background:#fbb;" | 9 || April 11 || @ Diamondbacks || 0–7 || Weaver (1–0) || De León (0–1) || — || 10,981 || 6–3 || L2 |-style="background:#bfb;" | 10 || April 12 || @ Giants || 3–0 || Miley (2–0) || Sanchez (0–1) || Sims (1) || 3,662 || 7–3 || W1 |-style="background:#fbb;" | 11 || April 13 || @ Giants || 6–7 || Peralta (2–0) || Pérez (1–1) || McGee (5) || 3,673 || 7–4 || L1 |-style="background:#fbb;" | 12 || April 14 || @ Giants || 0–3 || Cueto (2–0) || Mahle (1–1) || McGee (6) || 6,409 || 7–5 || L2 |-style="background:#bfb;" | 13 || April 16 || Indians || 10–3 || Hoffman (2–1) || Allen (1–2) || — || 12,497 || 8–5 || W1 |-style="background:#bfb;" | 14 || April 17 || Indians || 3–2 || Doolittle (2–0) || Pérez (0–1) || — || 12,598 || 9–5 || W2 |-style="background:#fbb;" | 15 || April 18 || Indians || 3–6 || Bieber (2–1) || Miley (2–1) || Clase (4) || 12,551 || 9–6 || L1 |-style="background:#bbb;" | — || April 20 || Diamondbacks || colspan=7| Suspended (Rain, continuation date: April 21) |-style="background:#fbb;" | 16 || April 21 || Diamondbacks || 4–5 || Bukauskas (1–0) || Garrett (0–1) || Crichton (2) || 8,085 || 9–7 || L2 |-style="background:#fbb;" | 17 || April 21 || Diamondbacks || 5–8 || Clarke (1–0) || Pérez (1–2) || — || 8,025 || 9–8 || L3 |-style="background:#fbb;" | 18 || April 22 || Diamondbacks || 11–14 || Smith (1–1) || Sims (0–1) || — || 7,549 || 9–9 || L4 |-style="background:#fbb;" | 19 || April 23 || @ Cardinals || 4–5 || Kim (1–0) || Gray (0–1) || Reyes (4) || 13,196 || 9–10 || L5 |-style="background:#fbb;" | 20 || April 24 || @ Cardinals || 0–2 || Gant (1–2) || Miley (2–2) || Gallegos (1) || 13,176 || 9–11 || L6 |-style="background:#fbb;" | 21 || April 25 || @ Cardinals || 2–5 || Flaherty (4–0) || Castillo (1–2) || Reyes (5) || 13,348 || 9–12 || L7 |-style="background:#bfb;" | 22 || April 26 || @ Dodgers || 5–3 || Antone (1–0) || Jansen (0–1) || — || 15,199 || 10–12 || W1 |-style="background:#bfb;" | 23 || April 27 || @ Dodgers || 6–5 || Hendrix (1–0) || Alexander (0–2) || Doolittle (1) || 15,306 || 11–12 || W2 |-style="background:#fbb;" | 24 || April 28 || @ Dodgers || 0–8 || Kershaw (4–2) || Gray (0–2) || — || 15,052 || 11–13 || L1 |-style="background:#bfb;" | 25 || April 30 || Cubs || 8–6 || Miley (3–2) || Arrieta (3–3) || Antone (1) || 16,090 || 12–13 || W1

|-style="background:#fbb;" | 26 || May 1 || Cubs || 2–3 || Brothers (1–0) || Castillo (1–3) || Kimbrel (5) || 17,077 || 12–14 || L1 |-style="background:#bfb;" | 27 || May 2 || Cubs || 13–12 || Hendrix (2–0) || Kimbrel (0–1) || — || 16,755 || 13–14 || W1 |-style="background:#fbb;" | 28 || May 4 || White Sox || 0–9 || Cease (2–0) || Hoffman (2–2) || — || 10,209 || 13–15 || L1 |-style="background:#bfb;" | 29 || May 5 || White Sox || 1–0 || Sims (1–1) || Hendriks (1–1) || — || 10,247 || 14–15 || W1 |-style="background:#bfb;" | 30 || May 7 || @ Indians || 3–0 || Miley (4–2) || Clase (2–2) || — || 7,803 || 15–15 || W2 |-style="background:#fbb;" | 31 || May 8 || @ Indians || 2–9 || Civale (5–0) || Castillo (1–4) || — || 9,968 || 15–16 || L1 |-style="background:#bbb;" | — || May 9 || @ Indians || colspan=7 | Postponed (make-up date August 9) |-style="background:#bfb;" | 32 || May 10 || @ Pirates || 14–1 || Mahle (2–1) || Keller (2–4) || — || 4,065 || 16–16 || W1 |-style="background:#fbb;" | 33 || May 11 || @ Pirates || 2–7 || Brubaker (3–2) || Hoffman (2–3) || — || 4,049 || 16–17 || L1 |-style="background:#bfb;" | 34 || May 12 || @ Pirates || 5–1 || Sims (2–1) || Underwood Jr. (1–2) || — || 4,515 || 17–17 || W1 |-style="background:#fbb;" | 35 || May 13 || @ Rockies || 8–13 || Gonzalez (2–1) || Castillo (1–5) || — || 13,647 || 17–18 || L1 |-style="background:#fbb;" | 36 || May 14 || @ Rockies || 6–9 || Márquez (2–4) || Miley (4–3) || Bard (4) || 20,232 || 17–19 || L2 |-style="background:#bfb;" | 37 || May 15 || @ Rockies || 6–5 || Sims (3–1) || Santos (0–1) || Hembree (1) || 20,136 || 18–19 || W1 |-style="background:#bfb;" | 38 || May 16 || @ Rockies || 7–6 || Doolittle (3–0) || Givens (1–2) || Antone (2) || 15,541 || 19–19 || W2 |-style="background:#fbb;" | 39 || May 17 || Giants || 3–6 || Webb (3–3) || Gray (0–3) || Rogers (5) || 11,004 || 19–20 || L1 |-style="background:#fbb;" | 40 || May 18 || Giants || 2–4 || DeSclafani (4–1) || Castillo (1–6) || McGee (11) || 8,745 || 19–21 || L2 |-style="background:#fbb;" | 41 || May 19 || Giants || 0–4 || Gausman (4–0) || Miley (4–4) || — || 10,326 || 19–22 || L3 |-style="background:#fbb;" | 42 || May 20 || Giants || 4–19 || Cueto (3–1) || Mahle (2–2) || — || 11,656 || 19–23 || L4 |-style="background:#bfb;" | 43 || May 21 || Brewers || 9–4 || Hoffman (3–3) || Houser (3–5) || — || 17,234 || 20–23 || W1 |-style="background:#fbb;" | 44 || May 22 || Brewers || 3–4 || Suter (3–2) || Hembree (0–1) || Hader (10) || 17,611 || 20–24 || L1 |-style="background:#fbb;" | 45 || May 23 || Brewers || 4–9 || Boxberger (1–1) || Castillo (1–7) || — || 16,171 || 20–25 || L2 |-style="background:#bfb;" | 46 || May 25 || @ Nationals || 2–1 || Mahle (3–2) || Scherzer (4–3) || Sims (2) || 8,935 || 21–25 || W1 |-style="background:#bbb;" | — || May 26 || @ Nationals || colspan=7 | Suspended (Inclement weather, Continuation May 27) |-style="background:#fbb;" | 47 || May 27 || @ Nationals || 3–5 || Voth (1–0) || Hoffman (3–4) || Hand (8) || 7,343 || 21–26 || L1 |-style="background:#bfb;" | 48 || May 27 || @ Nationals || 3–0 || Gray (1–3) || Strasburg (1–2) || Sims (3) || 9,020 || 22–26 || W1 |-style="background:#fbb;" | 49 || May 28 || @ Cubs || 0–1 || Alzolay (3–4) || Gutiérrez (0–1) || Kimbrel (12) || 18,478 || 22–27 || L1 |-style="background:#fbb;" | 50 || May 29 || @ Cubs || 2–10 || Thompson (3–1) || Castillo (1–8) || — || 24,275 || 22–28 || L2 |-style="background:#bfb;" | 51 || May 30 || @ Cubs || 5–1 || Mahle (4–2) || Arrieta (5–5) || Antone (3) || 24,824 || 23–28 || W1 |-style="background:#bfb;" | 52 || May 31 || Phillies || 11–1 || Miley (5–4) || Velasquez (2–1) || — || 17,878 || 24–28 || W2

|-style="background:#fbb;" | 53 || June 1 || Phillies || 3–17 || Nola (4–4) || Gray (1–4) || — || 10,788 || 24–29 || L1 |-style="background:#bbb;" | -- || June 2 || Phillies || colspan=7 | Postponed (make-up date June 28) |-style="background:#bfb;" | 54 || June 3 || @ Cardinals || 4–2 || Gutiérrez (1–1) || Wainwright (3–5) || Sims (4) || 15,327 || 25–29 || W1 |-style="background:#bfb;" | 55 || June 4 || @ Cardinals || 6–4 || Castillo (2–8) || Kim (1–4) || Feliz (1) || 22,756 || 26–29 || W2 |-style="background:#bfb;" | 56 || June 5 || @ Cardinals || 5–2 || Mahle (5–2) || Helsley (3–4) || Sims (5) || 23,365 || 27–29 || W3 |-style="background:#bfb;" | 57 || June 6 || @ Cardinals || 8–7 || Hembree (1–1) || Reyes (3–2) || Sims (6) || 21,152 || 28–29 || W4 |-style="background:#fbb;" | 58 || June 8 || Brewers || 1–5 || Houser (4–5) || Hendrix (2–1) || — || 11,897 || 28–30 || L1 |-style="background:#bfb;" | 59 || June 9 || Brewers || 7–3 || Gutiérrez (2–1) || Anderson (2–4) || — || 11,862 || 29–30 || W1 |-style="background:#fbb;" | 60 || June 10 || Brewers || 2–7 || Suter (7–3) || Castillo (2–9) || — || 12,423 || 29–31 || L1 |-style="background:#bfb;" | 61 || June 11 || Rockies || 11–5 || Mahle (6–2) || Freeland (0–2) || — || 20,505 || 30–31 || W1 |-style="background:#bfb;" | 62 || June 12 || Rockies || 10–3 || Miley (6–4) || Márquez (4–6) || — || 23,765 || 31–31 || W2 |-style="background:#bfb;" | 63 || June 13 || Rockies || 6–2 || Hendrix (3–1) || Senzatela (2–7) || — || 18,268 || 32–31 || W3 |-style="background:#bfb;" | 64 || June 14 || @ Brewers || 10–2 || Gutiérrez (3–1) || Lauer (1–3) || — || 17,127 || 33–31 || W4 |-style="background:#bfb;" | 65 || June 15 || @ Brewers || 2–1 || Sims (4–1) || Boxberger (2–2) || Garrett (3) || 16,584 || 34–31 || W5 |-style="background:#bfb;" | 66 || June 16 || @ Brewers || 2–1 || Mahle (7–2) || Peralta (6–2) || Sims (7) || 20,088 || 35–31 || W6 |-style="background:#fbb;" | 67 || June 17 || @ Padres || 4–6 || Johnson (2–2) || Garrett (0–2) || — || 40,362 || 35–32 || L1 |-style="background:#fbb;" | 68 || June 18 || @ Padres || 2–8 || Paddack (4–5) || Santillan (0–1) || — || 33,456 || 35–33 || L2 |-style="background:#fbb;" | 69 || June 19 || @ Padres || 5–7 || Crismatt (2–1) || Hembree (1–2) || Melancon (20) || 38,765 || 35–34 || L3 |-style="background:#fbb;" | 70 || June 20 || @ Padres || 2–3 || Lamet (2–2) || Castillo (2–10) || Melancon (21) || 38,004 || 35–35 || L4 |-style="background:#fbb;" | 71 || June 21 || @ Twins || 5–7 || Shoemaker (3–8) || Hembree (1–3) || — || 17,530 || 35–36 || L5 |-style="background:#bfb;" | 72 || June 22 || @ Twins || 10–7 || Antone (2–0) || Robles (3–4) || Garrett (4) || 19,187 || 36–36 || W1 |-style="background:#bfb;" | 73 || June 24 || Braves || 5–3 || Santillan (1–1) || Chavez (0–1) || Brach (1) || 23,941 || 37–36 || W2 |-style="background:#fbb;" | 74 || June 25 || Braves || 2–3 || Smyly (5–3) || Gutiérrez (3–2) || Smith (16) || 30,231 || 37–37 || L1 |-style="background:#bfb;" | 75 || June 26 || Braves || 4–1 || Castillo (3–10) || Anderson (5–4) || Garrett (5) || 34,671 || 38–37 || W1 |-style="background:#fbb;" | 76 || June 27 || Braves || 0–4 || Muller (1–1) || Mahle (7–3) || — || 21,696 || 38–38 || L1 |-style="background:#bfb;" | 77 || June 28 || Phillies || 12–4 || Hembree (2–3) || Feliz (0–1) || — || 21,006 || 39–38 || W1 |-style="background:#fbb;" | 78 || June 29 || Padres || 4–5 || Pagán (4–0) || Santillan (1–1) || Melancon (25) || 16,332 || 39–39 || L1 |-style="background:#fbb;" | 79 || June 30 || Padres || 5–7 || Musgrove (5–6) || Gutiérrez (3–3) || Hill (1) || 12,084 || 39–40 || L2