I believe it to be 3 (three) if it occurs in the ninth inning for the home team pitcher whose team has a lead, then the inning is complete without the home team having to pitch. Also a putout of any type would suffice, not just a ground-out. Other outs may qualify too, such as batting out of order, however it does not reduce the pitch count. The out of order batter must a have a minimum of 1 pitch.
27
3 by Nolan Ryan
3, many times.
Fifty-eight pitches, Red Barret of the Boston Braves against the Cinncinati Reds in a 2-0 complete game shutout, 1944.
I don't know what the ACTUAL fewest number of pitches is, but the fewest POSSIBLE is 27, one for each batter.
There are many pitchers who have made the fewest pitches in one inning. Three. Each batter swung at the first pitch and it resulted in an out. It still happens today, although it's usually four to six.
Pitch counts are spotty at best prior to the 1990s, but the record as far as we know is 74, by the Rockies' Aaron Cook on 7/25/07
112
102
Depends on how many pitches are thrown
Charley "Red" Barrett of the Boston Braves threw a grand total of 58 pitches in a MLB game on 1944 August 10.
in 1993 tanner regez threw 12 pitches to jimmy regez his brother.