Harold Joseph Wallis (born January 9, 1952) is an American former center fielder who spent five seasons in Major League Baseball with the Chicago Cubs and Oakland Athletics.

[2] He was selected by the Cubs in the sixth round of the 1973 MLB Draft.

Wallis broke up Tom Seaver's fifth attempt at his first-ever no-hitter with a two-out single to right field in the ninth inning of the Cubs' eleven-inning 1–0 win over the New York Mets at Wrigley Field on September 24, 1975.

The Indians then sent him to the Oakland Athletics for Gary Alexander an hour after the first transaction.

[4][5] Wallis finished his major league career with Oakland the following season.