Jacob Andrew Barnes (born April 14, 1990) is an American professional baseball pitcher who is a free agent.

He has played in Major League Baseball (MLB) for the Milwaukee Brewers, Kansas City Royals, Los Angeles Angels, New York Mets, Toronto Blue Jays, Detroit Tigers, New York Yankees, St. Louis Cardinals, and Washington Nationals.

After signing, Barnes made his professional debut with the Helena Brewers where he was 2–1 with a 2.12 ERA in 292⁄3 relief innings pitched.

After posting a 1.21 ERA over 17 games for the Sky Sox, the Brewers promoted Barnes to the major leagues on June 2, 2016.

In 2017, Barnes returned to Milwaukee and posted a 3–4 record and a 4.00 ERA in 73 relief appearances in his first full major league season.

In 19 appearances for the Mets, Barnes struggled to a 6.27 ERA in 182⁄3 innings of work before being designated for assignment on June 14, 2021.

[8] On June 19, 2021, Barnes was traded to the Toronto Blue Jays in exchange for Troy Miller.

[9] Barnes was designated for assignment by Toronto on July 26 after posting a 6.00 ERA in 9 appearances with the team.

On December 1, 2021, the Detroit Tigers signed Barnes to a minor league contract with an invitation to spring training.

On January 18, 2023, Barnes signed a minor league contract with the Texas Rangers organization.

[26] In 11 games for the Triple–A Lehigh Valley IronPigs, he posted a 4.15 ERA with 12 strikeouts and 1 save in 13 innings of work.

On August 22, the Cardinals selected Barnes' contract, adding him to the major league roster.

[31] After seven scoreless appearances for the Triple–A Rochester Red Wings, Barnes was added to Washington's major league roster on April 23.