The following are the baseball events of the year 1966 throughout the world.
Major league baseball final standings
American League final standings
National League final standings
- March 5 – In what will prove to be one of the more influential off-the-field events in Major League history, United Steelworkers union official Marvin Miller is elected the Executive Director of the Major League Baseball Players Association (MLBPA). Under Miller's guidance, the players' union will make major gains such as salary increases, improvements in pension benefits, and the advent of free agency and salary arbitration. Miller will occupy his position from 1966 to 1982, as the players' union was transformed into one of the strongest unions in the United States.
- March 8 – The Special Veterans Committee waives Hall of Fame election rules and inducts Casey Stengel, recently retired manager of the New York Mets.
- March 17 – Sandy Koufax and Don Drysdale escalate their threat of retirement by signing movie contracts. On March 30, they will end their 32-day holdout, signing for $130,000 and $105,000 respectively.
- May 7 – One day after the New York Yankees' record falls to 4–16, general manager Ralph Houk fires Johnny Keane as manager and returns to manage the team himself. Dan Topping, Jr. replaces Houk as general manager. Houk had managed the Yankees to three consecutive American League pennants from 1961 to 1963 and a World Series title during the first two of those years, but his second stint will have a far less than successful beginning. Their talent and farm system both depleted, the Yankees, after finishing in sixth place in 1965, will finish dead last—their first time doing so since 1912.
- May 8
- May 12 – With 46,048 spectators in attendance for the first game at the new Busch Memorial Stadium, the St. Louis Cardinals defeated the Atlanta Braves in 12 innings, 4–3, behind a single RBI by Lou Brock. Braves outfielder Felipe Alou delivered a pair of home runs.
- May 14 – The San Francisco Giants' Willie Mays hits his then National League record 512th home run – topping another Giant, Mel Ott. San Francisco beat the Los Angeles Dodgers, 6–1, at Candlestick Park.
- June 7 – The Kansas City Athletics use the second overall pick to draft Arizona State outfielder Reggie Jackson.
- June 9 – At Metropolitan Stadium, the Minnesota Twins rock the Kansas City Athletics, 9–4, with five home runs off the bats of Rich Rollins, Zoilo Versalles, Tony Oliva, Don Mincher and Harmon Killebrew in the seventh inning. These five home runs still stand as a Major League record for the most home runs batted in a single inning, and were hit off starter Catfish Hunter (two), reliever Paul Lindblad (two), and reliever John Wyatt.
- June 10 – Sonny Siebert of the Cleveland Indians no-hits the Washington Senators 2–0 at Cleveland Stadium. The no-hitter is the first by an Indian since Bob Feller's third career no-hitter, in 1951.
- July 3 – Atlanta pitcher Tony Cloninger hits two grand slams in a game against the Giants; he thus becomes the first National League player and only pitcher in Major League history to do so. His nine RBI in a game also is a record for pitchers.
- July 9 – Astroturf is finally installed in the Astrodome outfield.
- July 12 – At St. Louis, Maury Wills' 10th-inning single scores Tim McCarver, as the National League wins 2–1 over the American League in the All-Star Game, but AL Brooks Robinson's stellar game (three hits, eight fielding chances) earns him the MVP honors.
- July 21 – Against the Washington Senators in D.C., Minnesota Twins pitcher Jim Merritt strikes out twelve in a 1-0 shutout win. Seven of the twelve are consecutive, in the middle innings, to set an American League record. The final out in Merritt's string is his mound opponent Jim Hannan, who ironically had struck out Merritt just prior to the strikeout streak beginning.
- July 25 – During his Hall of Fame induction speech, Ted Williams publicly calls on baseball to induct former great players from the Negro Leagues. He specifically calls for the induction of Josh Gibson and Satchel Paige.
- July 27 – At Dodger Stadium, Sandy Koufax of the Los Angeles Dodgers faces Jim Bunning of the Philadelphia Phillies in the first matchup of perfect game pitchers. The Dodgers defeat the Phillies 2-1 in 12 innings with neither pitcher involved in the decision; both pitchers had pitched 11 innings with Koufax giving up four hits and striking out 16 and Bunning six hits and striking out 12.
- July 29 – Mickey Mantle homers against Bruce Howard of the White Sox. It is his 494th career home run and he passes Lou Gehrig for 6th place on the all-time list. The Yankees and Al Downing beat the Chicago White Sox, 2-1.
- August 15 – The Orioles left-handed slugger Boog Powell hits 3 opposite-field homers over the left-field Green Monster at Fenway Park. Powell has 13 total bases in the game, won by Baltimore, 4-2, in 11 innings.
- August 29 – The Detroit Tigers' Denny McLain wins his 16th start of the season, even though he doesn't do it that way. He throws 229 pitches, walks 9, and allows 8 hits. However, he strikes out 11 in a 6-3 win over the Baltimore Orioles.
- September 11 – Pat Jarvis became the first strikeout victim of Nolan Ryan's career.
- September 12 – Ron Perranoski of the Los Angeles Dodgers fans the first six batters he faces and earns a 3–2 win over the New York Mets. With the help of second baseman Ron Hunt, Mets rookie shortstop Bud Harrelson picks off Lou Johnson with the hidden ball trick in the sixth.
- September 18 – At Yankee Stadium, the New York Yankees fall to last place after losing to the Minnesota Twins 5-3 in 10 innings on pinch-hitter Bob Allison's three-run home run. The Yankees will stay in the cellar for the remainder of the season, finishing there for the first time since 1912.
- September 22 – The Baltimore Orioles beat the host Kansas City Athletics, 6–1, to clinch their first American League pennant since the St. Louis Browns moved to Baltimore. Both Brooks Robinson and Frank Robinson have two runs batted in. Frank Robinson will end the year as the Triple Crown winner, the first to achieve the feat since Mickey Mantle in 1956, after hitting a .316 batting average with 49 home runs and 122 RBI.
- September 25 – Against the Los Angeles Dodgers at Wrigley Field, in a battle of Jewish-American left-handers, Ken Holtzman of the Chicago Cubs has a no-hitter broken up on a Dick Schofield single leading off the ninth. Schofield later scores on a Maury Wills single; the two hits are all Holtzman allows in a 2–1 victory over the Dodgers in what will be Sandy Koufax's final regular-season loss. The Cubs score their two runs in the first as Don Kessinger, who had walked leading off the inning, scores on Glenn Beckert's triple one batter later; Beckert later scores as Jim Lefebvre drops Ernie Banks' pop-up for what would have been the third out.
- September 26 – Willie McCovey hits his 200th career home run, helping the San Francisco Giants beat the Atlanta Braves, 8–2.
- October 2 – In the second game of a doubleheader at Connie Mack Stadium, the Los Angeles Dodgers defeat the Philadelphia Phillies 6–3 as Sandy Koufax bests Jim Bunning in what will be the final regular-season game of Koufax's career. Despite giving up the three runs in the ninth inning, Koufax goes the distance and strikes out Jackie Brandt for the final out.
- October 9 – In Game Four of the World Series, Dave McNally wrapped up a brilliant pitching display, and the first World Series Championship for the Baltimore Orioles, with a four-hit, 1–0 shutout against the Los Angeles Dodgers. Series MVP Frank Robinson hits a home run off Don Drysdale for the only run of the game and gave Baltimore a sweep of the defending World Series Champion Dodgers. The shutout completes a World Series record 332⁄3 scoreless innings pitched by Orioles pitchers, beginning with Moe Drabowsky pitching 62⁄3 innings in relief of McNally in Game One, followed by shutouts by Jim Palmer and Wally Bunker—neither of whom had pitched a shutout during the regular season. The Orioles are the last of the original eight American League franchises to win their first World Series.
- December 1 – The Los Angeles Dodgers send former National League stolen base king Maury Wills to the Pittsburgh Pirates in exchange for infielders Bob Bailey and Gene Michael. Wills upset the Dodgers when he left the team during its recent tour of Japan.
- January 15 – Stover McIlwain, 26, pitcher for the Chicago White Sox from 1957 to 1958.
- January 15 – Walt Walsh, 66, Pinch runner for two games with the Philadelphia Phillies.
- January 29 – Homer Summa, 67, right fielder who collected a .302 average over 10 seasons with the Pittsburgh Pirates, Cleveland Indians and Philadelphia Athletics.
- February 14 – Jack Coffey, 79, infielder who played from 1909 to 1918 for the Boston Doves, Detroit Tigers and Boston Red Sox.
- March 18 – Frank Bennett, 61, pitcher for the Boston Red Sox in the 1920s.
- April 5 – Sam Dodge, 76, pitcher for the Boston Red Sox in the 1920s.
- April 12 – Joe Harris, 84, pitched with the Boston Americans in the early 20th century.
- May 4 – Bob Elliott, 49, 7-time All-Star third baseman who won the NL's 1947 MVP award.
- May 7 – Bing Miller, 71, outfielder for the Washington Senators, Philadelphia Athletics, St. Louis Browns and Boston Red Sox, who won two World Series with the Athletics in 1929 and 1930.
- June 27 – Marty Krug, 77, third baseman who played for the Boston Red Sox (1912) and Chicago Cubs (1922).
- July 9 – Mule Suttles, 66, All-Star first baseman of the Negro Leagues who hit the first home run in the East-West All-Star game.
- July 16 – Les Howe, 80, pitcher for the Boston Red Sox in the mid-1920s.
- August 1 – Hank Gowdy, 76, catcher and first baseman who won the 1914 World Series and is the only player to have served in both World Wars.
- August 10 – Chuck Dressen, 67, manager of five teams who led the Dodgers to pennants in 1952–53.
- August 15 – George J. Burns, 76, left fielder, primarily with the New York Giants, who led the NL in runs and walks five times each.
- August 17 – Bill Allington, 62, manager who won four Championship Titles in the All-American Girls Professional Baseball League.
- August 25 – Sam Zoldak, 47, pitcher for the St. Louis Browns, Cleveland Indians, and Philadelphia Athletics.
- August 29 – Al DeVormer, 75, catcher for the Chicago White Sox, New York Yankees, Boston Red Sox and New York Giants between 1918 and 1927.
- September 12 – Bill Summers, 70, American League umpire from 1933 to 1959 who worked in eight World Series and a record seven All-Star games.
- September 13 – Ralph Comstock, 75, pitched in the 1910s for the Detroit Tigers, Boston Red Sox, Pittsburgh Rebels, and Pittsburgh Pirates.
- October 4 – Mike Tresh, 52, catcher for the Chicago White Sox and Cleveland Indians from 1938 to 1949 and the father of New York Yankees slugger Tom Tresh.
- October 11 – Red Smith, 76, solid third baseman for multiple Dodgers and Braves teams in the 1910s, including the 1914 World Champions Boston Braves.
- October 17 – Bob Swift, 51, former catcher, coach, and acting manager of the Detroit Tigers, who caught the diminutive Eddie Gaedel in 1951.
- October 30 – Dick Barrett, 60, pitcher from 1933 to 1945 for the Athletics, Braves, Cubs and Phillies, who was named Minor League Player of the Year by The Sporting News in 1942.
- November 7 – Rube Bressler, 72, one of only a few players in major league baseball history to successfully convert from a pitcher to a position player as a first baseman/outfielder, who played for the Philadelphia Athletics & Phillies, Brooklyn Dodgers, Cincinnati Reds, and St. Louis Cardinals between 1914 and 1931.
- December 20 – Doc Farrell, 64, utility infielder for six different teams between 1925 and 1935, including the Yankees 1932 World Champions.