• National Association (professional):Athletic of Philadelphia
• National Association of Amateur Base Ball Players: Star of Brooklyn, 30–13
• National Association of Junior Base Ball Players: Fly Aways

The tenth founding member, theNational club of Washington, did not enter a team for the championship until1872.

• Ross Barnes of theBoston Red Stockings concludes in the top 5 in 11 different offensive categories. He leads the NA in runs scored, total bases and times on base. He is second in on-base percentage, doubles, triples and walks. He finishes third in batting average (.401) and hits. He places 4th in slugging percentage and 5th in runs batted in.
• Rynie Wolters of theNew York Mutuals leads the league in games started, complete games, and innings pitched and ties for the league lead with 1 shutout. He also leads the NA with 44 RBI while batting .370.

• January 20 – TheBoston Base Ball Club and theBoston Red Stockings are founded and incorporated byIvers Whitney Adams with $15,000 and the help ofHarry Wright, inBoston.
• March 17 – Ten clubs establish theNational Association of Professional Base Ball Players (or professional Association) in New York City.
• Later March – Thirty-three clubs establish the National Association of Amateur Base Ball Players (or amateur Association) in New York City.

• May 4 – In the first major league game ever played, the National Association begins play atKekionga Ball Grounds inFort Wayne,Indiana, withForest City of Cleveland visiting theKekiongas of Fort Wayne. Fort Wayne wins 2–0 behind the pitching ofBobby Mathews, the lowest scoring game of the season.Deacon White gets the first hit, whileJoe McDermott, who will only have 11 hits and four runs batted in his career, drives in the first run in professional baseball history with a single in the second inning, scoringBill Lennon. In the seventh inning, Lennon also became the first catcher in major league history to throw a runner out trying to steal second. Neither McDermott, Lennon, nor even the Kekiongas would finish the season.
• May 6 – Future Hall of FamerCap Anson makes his professional debut with theRockford Forest Citys.
• May 8 –Ezra Sutton of theCleveland Forest Citys hits the first home run in professional baseball history in the fourth inning against theChicago White Stockings. For good measure, Sutton adds a second home run in the seventh inning, but Cleveland falls to the White Stockings, 14–12.
• May 9 –Esteban Enrique Bellán becomes the first Hispanic player in Major League Baseball history. The 21-year-oldCuban infielder will play as Steve Bellan for theTroy Haymakers of the National Association.
• May 20 – InBoston,Mort Rogers introduces a scorecard with a picture ofHarry Wright on the front. EachRed Stockings home game would feature a different player so that spectators could collect them and have a full set of Boston's players by season's end. This marketing strategy would be used throughout the 19th century and would ultimately evolve intoTobacco cards and, eventually,Baseball cards.
• May 25 –Lip Pike of theTroy Haymakers collects six hits in a 25–10 victory over theNew York Mutuals.
• June 1 – Opening their National Association season, The Mutuals beat the Forest City club of Rockford,Illinois 7–3 before 2,000 atUnion Grounds inBrooklyn.
• June 19 – TheFort Wayne Kekiongas, leading theTroy Haymakers 6–3 after six innings at Troy, refuse to allow another ball to be used after the game ball becomes ripped because of the reputation of the Haymakers using illegal balls in the past. The umpire (Isaac Leroy or Ed Tighe depending on the source), after five full minutes of ordering Fort Wayne back on the field, calls the game a 9–0 forfeit in favor of the Haymakers.
• June 28 – In an era of high scoring games being the norm, thePhiladelphia Athletics defeat theTroy Haymakers by the amazing score of 49–33. Both pitchers go the distance in the four-hour slugfest in which both teams score in each inning, to set the highest-scoring contest inNational Association history. The 42hits made by the Athletics, including a 7-for-7 day byJohn Radcliff and 6-for-8 performances byAl Reach andLevi Meyerle, is also a league record.

• July 3 – TheNew York Mutuals lose atTroy 37–16. Even though it is customary to allow the visiting team to choose which ball to use, Troy captainBill Craver refuses to play unless their ball is used. Heated words are exchanged throughout, with the Mutuals even being threatened with bats. Mutuals captainBob Ferguson is convinced the ball used is not legal. This game will set the stage for the rematch on July 13 at theUnion Grounds inBrooklyn.
• July 6 – The first game between a black team and a white team is played as the black Uniques defeat the white Alerts 17–16 inChicago.
• July 10 –Albert Spalding is relieved byHarry Wright in theBoston Red Stockings 21–12 victory over theRockford Forest Citys after both Boston catchers develop sore hands from Spalding's fast pitching.
• July 13 –Brooklyn police are forced to draw their firearms to stop the crowd from attacking theTroy Haymakers following several altercations between the Haymakers and theNew York Mutuals players and officials after Troy's 9–7 win over the Mutuals.
• August 9 – Ned Connors, first baseman for theTroy Haymakers, records 20 putouts in a 9-inning 10–7 loss to theBrooklyn Eckfords.
• August 21 – The amateur champion Star Club ofBrooklyn beats the Northwest amateur champion Aetnas ofChicago 4–3 in Chicago as Star pitcherCandy Cummings drives in the winning run in the 9th inning.
• August 29 – TheBrooklyn Eckfords replace theFort Wayne Kekiongas in the NA after the Kekiongas lose most of their players to defection and expulsion. Fort Wayne's unplayed games will be declared forfeits in the official standings. The Eckfords will officially join theNational Association for the1872 season.
• September 5 –Charlie Gould of theBoston Red Stockings hits the first grand slam in professional baseball history in a 6–3 victory over theChicago White Stockings.

• October 9 – As theRockford Forest Citys approachChicago, they see the city in flames from theGreat Chicago Fire, turn around and go home. TheChicago White Stockings' stadium is burned to the ground along with all of their uniforms and equipment.
• October 18 – TheNew York Mutuals, with their only pitcherRynie Wolters sick, are forced to use a non-rostered position player,Frank Fleet, as pitcher in a crucial game for the pennant against thePhiladelphia Athletics. The Mutuals are battered 21–7 by the Athletics which eliminates theBoston Red Stockings from the championship.
• October 30 – TheAthletics of Philadelphia defeat theChicago White Stockings inBrooklyn 4–1 to clinch the first professional baseball championship.

• March 16 –Bill Bernhard
• March 19 –Joe McGinnity
• May 30 –Amos Rusie
• June 6 –Bill Lange
• July 15 –Dan McGann
• August 13 –Fielder Jones
• September 21 –George Blackburn
• October 24 –Louis Sockalexis
• October 24 –Heinie Smith
• October 25 –Martin Bergen
• October 30 –Buck Freeman
• November 3 –Fred Hayner
• November 26 –Fred Tenney
• December 9 –Joe Kelley
• December 23 –Sam Leever

• Wright, Marshall (2000).The National Association of Base Ball Players, 1857–1870. Jefferson, North Carolina: McFarland & Co.ISBN 0-7864-0779-4 (Postlude, p328-29)
• Ryczek, William J. (1992).Blackguards and Red Stockings; A History of Baseball's National Association 1871–1875. Wallingford, Connecticut: Colebrook PressISBN 0-9673718-0-5
• Orem, Preston D. (1961).Baseball (1845–1881) From the Newspaper Accounts. Altadena, California: Self-published.
• Charlton, James (1991).The Baseball Chronology. New York: MacmillanISBN 0-02-523971-6

• 1871 season at Baseball Reference.com
• Charlton's Baseball Chronology at BaseballLibrary.com
• Retrosheet.org

• 1871 in baseball

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• Short description matches Wikidata