Peter Michael "Pete" O'Brien (born February 9, 1958) is a former first baseman in Major League Baseball who played for the Texas Rangers (1982–88), Cleveland Indians (1989), and Seattle Mariners (1990–93).

[1] Neither drafted nor offered a scholarship out of high school, he played a year at Monterey Peninsula College and transferred to the University of Nebraska in Lincoln, then in the Big Eight Conference.

O'Brien made his major league debut with the Rangers in September 1982 at age 24 and won the starting job in 1983.

Forewarned by new manager Lou Piniella, the well-liked veteran was released on July 21 to make room on the roster for the returning Edgar Martínez.

The fathers of O'Brien and peer Kent Hrbek, first baseman of the Minnesota Twins, were afflicted with amyotrophic lateral sclerosis (ALS, or Lou Gehrig's disease) while their sons were playing in the major leagues.