The 1971 World Series matched the defending champions Baltimore Orioles against the Pittsburgh Pirates, with the Pirates winning in seven games. Game 4, played in Pittsburgh, was the first-ever World Series game scheduled to be played at night.
The two teams proved to be evenly matched, as the Series went the full seven games, with the Pirates' Steve Blass pitching a complete game four-hitter in winning Game 7, 2–1, against Mike Cuellar and the Orioles.
In what would be his final World Series appearance, The Pirates' Roberto Clemente became the first Spanish-speaking ballplayer to earn World Series MVP honors. Clemente hit safely in all seven games of the Series, duplicating a feat he had performed in 1960.
Bruce Kison, who appeared in two games and finished with 6.1 innings pitched, tied the record set during the 1907 World Series when he hit three batters during a single series.
These two teams would meet again in the fall classic eight years later, with the same result.
The Pirates won the National League East by seven games over the St. Louis Cardinals then defeated the San Francisco Giants, three games to one, in the National League Championship Series. The Orioles won the American League East by 12 games over the Detroit Tigers then swept the Oakland A's in the American League Championship Series.
The Orioles were coming off their third straight AL playoff series sweep (twice over the Minnesota Twins, once over the Oakland A's) and their third straight season with over 100 wins (1969 — 109, 1970 — 108, 1971 — 101). Featuring four (4) pitchers with 20 or more wins (Dave McNally — 21, Mike Cuellar — 20, Pat Dobson — 20, Jim Palmer — 20), the booming bats of sluggers Frank Robinson (28, 99, .281) and Boog Powell (22, 92, .256), and the sure hands of Brooks Robinson at third and Mark Belanger at short, the O's were primed to defend their title.
The Pirates were in the World Series for the first time since the heroics of Bill Mazeroski (who appeared in this series as a pinch-hitter in Game 1) in Game 7 of the 1960 match-up against the New York Yankees. Though not as decorated as the O's staff, the Pirates featured 19-game winner Dock Ellis and 15-game winner Steve Blass. The Bucs did boast a murderous lineup led by Willie Stargell (48, 125, .295), Bob Robertson (26, 72, .271) and Roberto Clemente (13, 86, .341), who collected 12 series hits and hit .414.
NL Pittsburgh Pirates (4) vs. AL Baltimore Orioles (3)
†: postponed from October 10 due to rain
The Pirates scored three in the second thanks to some unusually sloppy defense by the Orioles. Bob Robertson led off with a walk and went to second on a wild pitch by O's starter Dave McNally. Manny Sanguillén grounded to short, but Mark Belanger threw wildly to third in an attempt to retire Robertson. Robertson scored and Sanguillen pulled in at second. After Sanguillen was grounded to third by José Pagán, Jackie Hernández laid down a suicide squeeze bunt to score Sanguillen and went to second when catcher Elrod Hendricks threw wildly to first. Dave Cash singled home Hernandez with the only hit the Pirates got the whole inning among the three runs.
To atone for the bad defense, the Orioles clawed back with their power hitting. Frank Robinson hit a homer in the second and Merv Rettenmund blasted a three-run homer in the third off Dock Ellis to give the Orioles the lead. Don Buford added a homer in the fifth as McNally settled down and allowed only two more hits and no runs the rest of the way.
Following a one-day delay caused by a rainout, the Orioles took a 2–0 lead by pounding six Pirate pitchers for fourteen hits and eleven runs, led by three hits and four RBIs by Brooks Robinson. Jim Palmer pitched seven shutout innings and helped himself the easy way by drawing two bases-loaded walks for two RBIs. The Pirates got their runs in the eighth when Richie Hebner hit a three-run homer off Palmer.
With the Series shifting to Three Rivers Stadium and with Steve Blass available, the Pirates got back into it. Blass pitched a complete game, allowing only three hits and one run (on a Frank Robinson homer) and striking out eight. The big blow on offense was provided by Bob Robertson, who slammed a three-run homer in the seventh off starter Mike Cuellar—after missing the bunt sign. Manager Danny Murtaugh issued the sign to Robertson, who had no sacrifice bunts on the season. Television replays showed Roberto Clemente, who was on second base, appearing to call a timeout, but Cuellar was already in his windup at the time. Blass was sitting next to Murtaugh in the dugout at the time, and told the Pirate manager: "If you fine him (Robertson, for missing the bunt sign), I'll pay." Murtaugh didn't. 
In the first ever night game in World Series history, it started out looking like a long night for the Pirates. Starting pitcher Luke Walker gave up singles to the Orioles' first three batters, Paul Blair, Mark Belanger, and Merv Rettenmund, loading the bases. Blair scored and the others advanced on a Manny Sanguillén passed ball. Walker then intentionally walked Frank Robinson and gave up consecutive sacrifice flies to Brooks Robinson and Boog Powell, giving the Orioles a 3–0 lead.
Manager Danny Murtaugh then pulled Walker in favor of Bruce Kison. Kison proceeded to get the final out of the inning and then pitched shutout baseball for the next six innings, allowing only one hit and despite hitting three Oriole batters, a World Series record.
Kison's heroics allowed the Pirates to claw back. Willie Stargell and Al Oliver cut the lead to 3–2 in the bottom of the first with back-to-back RBI doubles. Oliver tied the score at 3 in the third with an RBI single.
In the seventh, Bob Robertson and Sanguillen stroked one-out singles off reliever Eddie Watt. Pinch-hitter Vic Davalillo then lofted a short fly to center that Paul Blair dropped. Robertson reached third and Davalillo first, but Sanguillen was caught in a rundown between second and third. Backup catcher Milt May then batted for Kison and delivered a clutch go-ahead RBI single, scoring Robertson.
Dave Giusti pitched the final two innings of hitless ball for the Pirates and got the save.
Danny Murtaugh wanted to save his two ace pitchers, Steve Blass and Dock Ellis, for Games 6 and 7 (if necessary), so he went with spot starter/reliever Nelson Briles in this game. The gamble paid off as Briles pitched a gem, a complete game two-hit shutout. Briles himself had an RBI single in the win and Bob Robertson homered. Roberto Clemente got his first RBI of the series in this one as well, an RBI single in the fifth.
The series shifted back to Baltimore with the Orioles facing elimination. With Steve Blass needing another day of rest and Dock Ellis nursing an injury, Danny Murtaugh had to go to the well once again, starting reliever Bob Moose—his sixth different starter in this Series. Moose responded well by pitching shutout ball for five innings, while his Pirate teammates got him a 2–0 lead. Al Oliver doubled in the second off Jim Palmer and scored on a Bob Robertson single. Roberto Clemente added a homer in the third.
Moose started having trouble in the sixth, however. Don Buford belted a one-out homer and Moose allowed the next two batters to reach base before giving way to Bob Johnson, who ended the threat. The Orioles tied it off Johnson in the seventh when Mark Belanger singled, stole second, and scored on a single by Davey Johnson.
Both teams threatened late; the Orioles had runners on second and third in the bottom of the ninth with two out, but failed to score. The Pirates loaded the bases in the top of the tenth, but Dave McNally, pitching in relief, squelched the threat.
The Orioles staved off a World Series defeat in their half of the tenth when Frank Robinson drew a one-out walk and went to third on a Merv Rettenmund single. Brooks Robinson lifted a short fly to center and Frank Robinson tagged and scored the winning run, barely beating Vic Davalillo's throw to the plate.
With ace pitchers Steve Blass and Mike Cuellar on the mound for their respective teams, Game 7 proved to be a pitcher's duel.
Series MVP Roberto Clemente drew first blood for the Pirates by hitting a two-out homer in the fourth off Cuellar. The Pirates added another run in the eighth when José Pagán doubled in Willie Stargell.
The only run the O's could muster off Blass was an RBI groundout by Don Buford in the eighth. Blass would get his second complete game win of the series.
Game 7 was the only game in which the visiting team won.
1971 World Series (4–3): Pittsburgh Pirates (N.L.) over Baltimore Orioles (A.L.)