Offseason

• November 29, 1965: 1965 rule 5 draft
  Rule 5 draft
  The Rule 5 draft is a Major League Baseball player draft that occurs each year in December, at the annual Winter Meeting of general managers. The Rule 5 draft aims to prevent teams from stockpiling too many young players on their minor league affiliate teams when other teams would be willing to...
  
  
  • Nate Colbert
    Nate Colbert
    Nathan Colbert Jr. , is a former American Major League Baseball player who was a first baseman with the Houston Astros , San Diego Padres , Detroit Tigers , Montreal Expos and Oakland Athletics .Signed by his hometown St...
    
     was drafted by the Astros from the St. Louis Cardinals
    St. Louis Cardinals
    The St. Louis Cardinals are a professional baseball team based in St. Louis, Missouri. They are members of the Central Division in the National League of Major League Baseball. The Cardinals have won eleven World Series championships, the most of any National League team, and second overall only to...
    
    .
  • Bob Saverine
    Bob Saverine
    Robert Paul Saverine is a former Major League Baseball infielder/outfielder. He was signed by the Baltimore Orioles as an amateur free agent before the 1959 season and played for the Orioles and the Washington Senators...
    
     was drafted from the Astros by the Washington Senators
    Texas Rangers (baseball)
    The Texas Rangers are a professional baseball team in the Dallas-Fort Worth Metroplex, based in Arlington, Texas. The Rangers are a member of the Western Division of Major League Baseball's American League, and are the reigning A.L. Western Division and A.L. Champions. Since , the Rangers have...
    
    .
• January 6, 1966: Johnny Weekly
  Johnny Weekly
  Johnny Weekly was a Major League Baseball player. Weekly played for the Houston Colt .45s from to . He batted and threw right-handed.He was born in Waterproof, Louisiana and died in Walnut Creek, California....
  
   and cash were traded by the Astros to the New York Mets
  New York Mets
  The New York Mets are a professional baseball team based in the borough of Queens in New York City, New York. They belong to Major League Baseball's National League East Division. One of baseball's first expansion teams, the Mets were founded in 1962 to replace New York's departed National League...
  
   for Gary Kroll
  Gary Kroll
  Gary Melvin Kroll is an American former Major League Baseball pitcher who played for four seasons. The , righthander played for the Philadelphia Phillies in 1964, the New York Mets from 1964 to 1965, the Houston Astros in 1966, and the Cleveland Indians in 1969...
  
  .

Opening Day lineup

1. Lee Maye
   Lee Maye
   Arthur Lee Maye was a Major League Baseball player. He played eleven seasons in the majors as an outfielder for the Milwaukee Braves , Houston Astros , Cleveland Indians , Washington Senators , and Chicago White Sox .Maye was also well known as a Rhythm & Blues singer...
   
   , LF
2. Sonny Jackson, SS
3. Jimmy Wynn
   Jimmy Wynn
   James Sherman Wynn , nicknamed the "Toy Cannon," is a former Major League Baseball center fielder. During a 15-year baseball career, he played from 1963-1977 for five different teams: the Houston Colt .45s/Astros, Los Angeles Dodgers, Atlanta Braves, New York Yankees, and Milwaukee Brewers...
   
   , CF
4. Dave Nicholson
   Dave Nicholson
   David Lawrence Nicholson is a former outfielder for the Baltimore Orioles , Chicago White Sox , Houston Astros and Atlanta Braves , known for his towering, although infrequent, home runs...
   
   , RF
5. Joe Morgan
   Joe Morgan
   Joe Leonard Morgan is a former Major League Baseball second baseman who played for the Houston Astros, Cincinnati Reds, San Francisco Giants, Philadelphia Phillies, and Oakland Athletics from 1963 to 1984. He won two World Series championships with the Reds in 1975 and 1976 and was also named the...
   
   , 2B
6. Bob Aspromonte
   Bob Aspromonte
   Robert Thomas Aspromonte is a former utility player who had a 13 year career in 1956 and from 1960 to 1971. He played for the Brooklyn/Los Angeles Dodgers, Houston Colt 45's/Astros, Atlanta Braves and New York Mets all of the National League.During his career, Aspromonte played first base, second...
   
   , 3B
7. Chuck Harrison
   Chuck Harrison (baseball)
   Charles William Harrison is a retired American professional baseball player. He was a first baseman in Major League Baseball who played between through for the Houston Astros and Kansas City Royals . Listed at , , Harrison batted and threw right-handed...
   
   , 1B
8. John Bateman, C
9. Robin Roberts, P

Notable transactions

• June 7, 1966: Fred Stanley was drafted by the Astros in the 8th round of the 1966 Major League Baseball Draft
  1966 Major League Baseball Draft
  -First round selections:The following are the first round picks in the 1966 Major League Baseball draft.* Did not sign- Background :A January free agent amateur draft was added for the first time in 1966. Ninety-five prospects were selected in the regular phase and 102 in the secondary phase of the...
  
  .

Roster

Starters by position

Other batters

Starting pitchers

Other pitchers

Relief pitchers

Farm system