The 1981 Montreal Expos season was the 13th season in franchise history. They made it to the postseason for the first time in franchise history. Their playoff run ended in the NLCS against the Los Angeles Dodgers, with Rick Monday hitting a ninth-inning solo home run in game 5, subsequently referred to as "Blue Monday" by Expos fans. This was the closest the Expos ever got to a World Series appearance while in Montreal. This was also their last time winning a playoff series until 2019, which they won the Wild Card game. The season was separated into two halves due to the 1981 Major League Baseball strike.

This would be the first and only time the team made the postseason as the Montreal Expos. The next time the franchise would reach the playoffs was in the 2012 season, after relocating to Washington, D.C., and becoming the Washington Nationals. The 30-year postseason drought set a Major League Baseball record for the longest in MLB history.

Offseason December 8, 1980: Jack O'Connor was drafted from the Expos by the Minnesota Twins in the rule 5 draft. December 12, 1980: Tony Bernazard was traded by the Expos to the Chicago White Sox for Rich Wortham. December 12, 1980: Willie Montañez was signed as a free agent by the Expos. January 15, 1981: Ken Macha was purchased from the Expos by the Toronto Blue Jays. February 18, 1981: Ray Burris was signed as a free agent by the Expos.

Spring training After holding spring training at City Island Ball Park in Daytona Beach, Florida, from 1973 to 1980, the Expos returned to West Palm Beach Municipal Stadium in West Palm Beach, Florida – a facility they shared with the Atlanta Braves – for spring training in 1981. It was their fifth season at the stadium; they also had conducted spring training there from 1969 to 1972. The Expos would train at Municipal Stadium through 1997.

Regular season April 29, 1981: Steve Carlton struck out Tim Wallach for the 3000th strikeout of his career. May 10, 1981: Charlie Lea pitched a no-hitter against the San Francisco Giants, defeating them 4–0 at Olympic Stadium. The last out was recorded by Andre Dawson in center field. Lea would go on to shut out the Giants again a week later on four hits in San Francisco for good measure.

Game log

First half

|- style="text-align:center; background:#bfb;" | 1 || April 9 || @ Pirates || 6–5 || Fryman (1–0) || Tekulve (0–1) || || 40,332 || 1–0 || Boxscore |- style="text-align:center; background:#fbb;" | 2 || April 12 || @ Pirates || 2–3 || Rhoden (1–0) || Burris (0–1) || Romo (1) || 8,430 || 1–1 || Boxscore |- style="text-align:center; background:#bfb;" | 3 || April 15 || Cubs || 5–4 || Bahnsen (1–0) || Tidrow (1–1) || || 30,003 || 2–1 || Boxscore |- style="text-align:center; background:#bfb;" | 4 || April 16 || Cubs || 7–0 || Sanderson (1–0) || McGlothen (0–1) || || 11,602 || 3–1 || Boxscore |- style="text-align:center; background:#bfb;" | 5 || April 18 || @ Mets || 5–3 || Gullickson (1–0) || Jones (0–1) || Bahnsen (1) || 23,710 || 4–1 || Boxscore |- style="text-align:center; background:#bfb;" | 6 || April 19 || @ Mets || 4–3 || Burris (1–1) || Swan (0–1) || Fryman (1) || N/A || 5–1 || Boxscore |- style="text-align:center; background:#fbb;" | 7 || April 19 || @ Mets || 2–7 || Zachry (3–0) || Lea (0–1) || || 21,464 || 5–2 || Boxscore |- style="text-align:center; background:#bfb;" | 8 || April 20 || Phillies || 9–8 || Rogers (1–0) || McGraw (1–1) || Fryman (2) || 24,817 || 6–2 || Boxscore |- style="text-align:center; background:#bfb;" | 9 || April 21 || Phillies || 10–3 || Sanderson (2–0) || Ruthven (2–1) || || 10,887 || 7–2 || Boxscore |- style="text-align:center; background:#bfb;" | 10 || April 22 || Phillies || 4–3 (11 inn.) || Sosa (1–0) || McGraw (1–2) || || 14,176 || 8–2 || Boxscore |- style="text-align:center; background:#bbb;" | || April 24 || Mets || colspan=7 |Postponed (rain); rescheduled for April 26 |- style="text-align:center; background:#bfb;" | 11 || April 25 || Mets || 4–2 || Rogers (2–0) || Jones (0–2) || Lee (1) || 18,150 || 9–2 || Boxscore |- style="text-align:center; background:#bfb;" | 12 || April 26 || Mets || 8–4 || Burris (2–1) || Zachry (3–1) || || N/A || 10–2 || Boxscore |- style="text-align:center; background:#bfb;" | 13 || April 26 || Mets || 7–6 || Sanderson (3–0) || Swan (0–2) || Fryman (3) || 41,697 || 11–2 || Boxscore |- style="text-align:center; background:#fbb;" | 14 || April 27 || @ Phillies || 1–3 || Ruthven (3–1) || Gullickson (1–1) || || 27,347 || 11–3 || Boxscore |- style="text-align:center; background:#bfb;" | 15 || April 28 || @ Phillies || 6–3 || Ratzer (1–0) || Christenson (1–2) || Sosa (1) || 26,192 || 12–3 || Boxscore |- style="text-align:center; background:#fbb;" | 16 || April 29 || @ Phillies || 2–6 || Carlton (4–0) || Rogers (2–1) || || 30,142 || 12–4 || Boxscore

|- style="text-align:center; background:#bfb;" | 17 || May 1 || Dodgers || 9–8 (13 inn.) || Lee (1–0) || Castillo (0–2) || || 28,179 || 13–4 || Boxscore |- style="text-align:center; background:#fbb;" | 18 || May 2 || Dodgers || 0–4 || Reuss (2–1) || Sanderson (3–1) || || 22,820 || 13–5 || Boxscore |- style="text-align:center; background:#fbb;" | 19 || May 3 || Dodgers || 1–6 (10 inn.) || Valenzuela (6–0) || Gullickson (1–2) || || 46,405 || 13–6 || Boxscore |- style="text-align:center; background:#bfb;" | 20 || May 4 || Dodgers || 4–3 || Rogers (3–1) || Sutcliffe (2–2) || Sosa (2) || 21,527 || 14–6 || Boxscore |- style="text-align:center; background:#bfb;" | 21 || May 5 || Padres || 4–3 || Fryman (2–0) || || || 15,909 || 15–6 || Boxscore |- style="text-align:center; background:#fbb;" | 22 || May 6 || Padres || 5–13 || || Burris (2–2) || || 13,066 || 15–7 || Boxscore |- style="text-align:center; background:#bfb;" | 23 || May 7 || Padres || 2–1 || Sanderson (4–1) || || || 12,248 || 16–7 || Boxscore |- style="text-align:center; background:#fbb;" | 24 || May 8 || Giants || 3–4 || || Gullickson (1–3) || || 21,850 || 16–8 || Boxscore |- style="text-align:center; background:#fbb;" | 25 || May 9 || Giants || 2–8 || || Rogers (3–2) || || 48,149 || 16–9 || Boxscore |- style="text-align:center; background:#fbb;" | 26 || May 10 || Giants || 1–5 || || Lee (1–1) || || N/A || 16–10 || Boxscore |- style="text-align:center; background:#bfb;" | 27 || May 10 || Giants || 4–0 || Lea (1–1) || || || 25,343 || 17–10 || Boxscore |- style="text-align:center; background:#fbb;" | 28 || May 12 || @ Dodgers || 0–5 || Hooton (5–0) || Burris (2–3) || Howe (4) || 34,367 || 17–11 || Boxscore |- style="text-align:center; background:#fbb;" | 29 || May 13 || @ Dodgers || 6–8 || Howe (2–1) || Fryman (2–1) || || 42,712 || 17–12 || Boxscore |- style="text-align:center; background:#fbb;" | 30 || May 14 || @ Dodgers || 2–3 || Valenzuela (8–0) || Ratzer (1–1) || || 53,906 || 17–13 || Boxscore |- style="text-align:center; background:#fbb;" | 31 || May 15 || @ Giants || 2–4 || || Rogers (3–3) || || 19,763 || 17–14 || Boxscore |- style="text-align:center; background:#bfb;" | 32 || May 16 || @ Giants || 5–0 || Lea (2–1) || || || 11,133 || 18–14 || Boxscore |- style="text-align:center; background:#fbb;" | 33 || May 17 || @ Giants || 4–5 (12 inn.) || || Lee (1–2) || || 27,975 || 18–15 || Boxscore |- style="text-align:center; background:#bfb;" | 34 || May 18 || @ Padres || 3–2 (10 inn.) || Fryman (3–1) || || Lee (2) || 13,283 || 19–15 || Boxscore |- style="text-align:center; background:#fbb;" | 35 || May 19 || @ Padres || 1–3 || || Gullickson (1–4) || || 6,871 || 19–16 || Boxscore |- style="text-align:center; background:#bfb;" | 36 || May 20 || @ Padres || 6–2 || Rogers (4–3) || || || 9,336 || 20–16 || Boxscore |- style="text-align:center; background:#bfb;" | 37 || May 22 || @ Cubs || 6–3 || Lea (3–1) || Krukow (1–5) || || 6,071 || 21–16 || Boxscore |- style="text-align:center; background:#fbb;" | 38 || May 23 || @ Cubs || 4–6 || Reuschel (2–5) || Burris (2–4) || Tidrow (2) || 15,981 || 21–17 || Boxscore |- style="text-align:center; background:#fbb;" | 39 || May 24 || @ Cubs || 2–6 || Caudill (1–3) || Sanderson (4–2) || Tidrow (3) || 10,821 || 21–18 || Boxscore |- style="text-align:center; background:#bfb;" | 40 || May 25 || Cardinals || 5–3 || Gullickson (2–4) || || Lee (3) || 24,490 || 22–18 || Boxscore |- style="text-align:center; background:#bfb;" | 41 || May 26 || Cardinals || 4–3 || Rogers (5–3) || || Sosa (3) || 27,775 || 23–18 || Boxscore |- style="text-align:center; background:#bfb;" | 42 || May 27 || Cardinals || 4–1 || Lea (4–1) || || Lee (4) || 24,709 || 24–18 || Boxscore |- style="text-align:center; background:#bfb;" | 43 || May 29 || Pirates || 3–2 || Sanderson (5–2) || Bibby (3–3) || Lee (5) || 36,662 || 25–18 || Boxscore |- style="text-align:center; background:#fbb;" | 44 || May 30 || Pirates || 2–3 || Rhoden (6–0) || Gullickson (2–5) || || 31,649 || 25–19 || Boxscore |- style="text-align:center; background:#bfb;" | 45 || May 31 || Pirates || 5–1 || Rogers (6–3) || Pérez (2–1) || || 45,783 || 26–19 || Boxscore

|- style="text-align:center; background:#fbb;" | 46 || June 1 || @ Cardinals || 2–4 || || Lea (4–2) || || 14,224 || 26–20 || Boxscore |- style="text-align:center; background:#bfb;" | 47 || June 2 || @ Cardinals || 8–1 || Burris (3–4) || || || 14,697 || 27–20 || Boxscore |- style="text-align:center; background:#fbb;" | 48 || June 3 || @ Cardinals || 2–3 (11 inn.) || || Sosa (1–1) || || 13,085 || 27–21 || Boxscore |- style="text-align:center; background:#fbb;" | 49 || June 4 || @ Cardinals || 1–4 || || Gullickson (2–6) || || 18,958 || 27–22 || Boxscore |- style="text-align:center; background:#fbb;" | 50 || June 5 || @ Reds || 3–6 || || Rogers (6–4) || || || 27–23 || Boxscore |- style="text-align:center; background:#fbb;" | 51 || June 6 || @ Reds || 3–9 || || Lea (4–3) || || || 27–24 || Boxscore |- style="text-align:center; background:#fbb;" | 52 || June 7 || @ Reds || 0–2 || || Burris (3–5) || || || 27–25 || Boxscore |- style="text-align:center; background:#bfb;" | 53 || June 9 || Braves || 12–1 || Sanderson (6–2) || || || || 28–25 || Boxscore |- style="text-align:center; background:#bfb;" | 54 || June 10 || Braves || 11–2 || Gullickson (3–6) || || || || 29–25 || Boxscore |- style="text-align:center; background:#bfb;" | 55 || June 11 || Braves || 7–0 || Rogers (7–4) || || || || 30–25 || Boxscore

Games cancelled

|- style="text-align:center; background:#bbb;" | || April 11 || @ Pirates || colspan=7 |Cancelled (strike) |- style="text-align:center; background:#bbb;" | || April 14 || Cubs || colspan=7 |Cancelled (strike)

|- style="text-align:center; background:#bbb;" | || June 12 || Reds || colspan=7 |Cancelled (strike) |- style="text-align:center; background:#bbb;" | || June 13 || Reds || colspan=7 |Cancelled (strike) |- style="text-align:center; background:#bbb;" | || June 14 || Reds || colspan=7 |Cancelled (strike) |- style="text-align:center; background:#bbb;" | || June 15 || Astros || colspan=7 |Cancelled (strike) |- style="text-align:center; background:#bbb;" | || June 16 || Astros || colspan=7 |Cancelled (strike) |- style="text-align:center; background:#bbb;" | || June 17 || @ Braves || colspan=7 |Cancelled (strike) |- style="text-align:center; background:#bbb;" | || June 18 || @ Braves || colspan=7 |Cancelled (strike) |- style="text-align:center; background:#bbb;" | || June 19 || @ Astros || colspan=7 |Cancelled (strike) |- style="text-align:center; background:#bbb;" | || June 20 || @ Astros || colspan=7 |Cancelled (strike) |- style="text-align:center; background:#bbb;" | || June 21 || @ Astros || colspan=7 |Cancelled (strike) |- style="text-align:center; background:#bbb;" | || June 23 || Mets || colspan=7 |Cancelled (strike) |- style="text-align:center; background:#bbb;" | || June 24 || Mets || colspan=7 |Cancelled (strike) |- style="text-align:center; background:#bbb;" | || June 25 || Mets || colspan=7 |Cancelled (strike) |- style="text-align:center; background:#bbb;" | || June 26 || Cubs || colspan=7 |Cancelled (strike)