Aaron Samuel Altherr (/ɑːlˈtɛər/ ahl-TAIR; born January 14, 1991) is a German-American professional baseball outfielder for the Algodoneros de Unión Laguna of the Mexican League.

Altherr has played in Major League Baseball (MLB) for the Phillies, San Francisco Giants, and New York Mets.

Altherr was born in Germany, where his mother, Michelle, a member of the United States Air Force, was stationed.

[5] Altherr began 2010 back with the GCL team, where in 27 games, he hit .304 with 15 RBI and 10 SB, but he struck out 22 times to just 3 walks.

By the time the New York–Penn League began in 2011, he was back with Williamsport, but he understood the demotion and worked to regain his confidence.

He played 2013 with High-A Clearwater, where in 123 games, he hit .275 with 12 HR, 69 RBI and 23 SB, but he struck out 140 times.

[11] He made his major league debut that night, appearing as a pinch-hitter in the 12th inning against the Atlanta Braves.

[13] After splitting the first four months of 2015 season between Reading and the Triple-A Lehigh Valley IronPigs, he was recalled to Philadelphia on August 18.

[14] The following day, he recorded his first Major League hit, an RBI double against Mark Buehrle of the Toronto Blue Jays.

On September 25, Altherr hit an inside-the-park grand slam off Jordan Zimmermann in an 8–2 win over the Washington Nationals, driving in Brian Bogusevic, Cameron Rupp, and Jerad Eickhoff.

[15] During spring training in 2016, Altherr tore a ligament in his left wrist, requiring surgery that caused him to miss the first half of the season.

[17] On September 18, 2017, in a 4–3 win over the Los Angeles Dodgers, Altherr hit a grand slam, the first one ever given up by Clayton Kershaw, who was then making his 288th regular-season start, having pitched 1,917 innings in 10 seasons.

[20] On July 22, 2018, Altherr was sent down to the Phillies Triple A Lehigh Valley Iron Pigs, but was brought back up in September.

[22] On April 10, 2019, in the ninth inning of a game where the Washington Nationals were blowing out the Phillies 14–0, Altherr was called upon to pitch.

[40] Altherr was born in Landstuhl, Germany, where his mother, Michelle, a native of Baltimore, was stationed as a member of the United States Air Force.