Jack William Armstrong (born March 7, 1965) is an American former Major League Baseball right-handed pitcher who played for several teams between 1988 and 1994.

In 1986, he was MVP of the CCBL all-star game, and received the league's Outstanding Pitcher award.

He relieved Scott Scudder in Game 2 of the 1990 World Series with the Reds trailing, 4–3.

His son, Jack Armstrong Jr., turned down a $1 million signing bonus from the Texas Rangers out of high school in order to play college baseball for the Vanderbilt Commodores.

[citation needed] Erik, his younger son, played baseball at the University of South Carolina Beaufort.