John Albert Pfiester (May 24, 1878 – September 3, 1953) was an American professional baseball pitcher.

Born in Cincinnati, Ohio, Pfiester started his professional baseball career in the minor leagues in 1901.

As soon as the game ended, he went to Ohio to be treated, and his tendon was snapped back into place by trainer Bonesetter Reese.

After National League President Harry Pulliam ruled the Merkle's Boner game to have ended in a tie, Pfeister was called upon by Cubs manager Frank Chance to start the makeup game on October 8 in New York.

Pfeister gave up a run in less than an inning of work before Chance had seen enough and called in Mordecai Brown, who held the Giants to just one run the rest of the way, ensuring a 4–2 Cubs triumph to capture the NL pennant.

His career ERA in MLB was 2.02, which is the fourth-lowest of all time among pitchers with at least 1,000 innings thrown.