Christian Koss

Christian Koss (born January 27, 1998) is an American professional baseball infielder for the San Francisco Giants of Major League Baseball (MLB). He made his MLB debut in 2025.

Early life Koss was born and grew up in Riverside, California, and attended John W. North High School. Koss attended the University of California, Irvine, and played college baseball for the UC Irvine Anteaters for three seasons. Following his freshman and sophomore seasons, he played collegiate summer baseball with the Yarmouth–Dennis Red Sox of the Cape Cod Baseball League and was named a league All-Star in 2018. Koss batted .307 with five home runs and 30 RBI in 54 games as a junior. Koss did not play in a game in 2020 due to the cancellation of the minor league season because of the COVID-19 pandemic.

Boston Red Sox On December 4, 2020, Koss was traded to the Boston Red Sox in exchange for Yoan Aybar. Koss spent the 2021 season with the High-A Greenville Drive and batted .271/.325/.451 with 15 home runs, 55 RBI, and 10 stolen bases across 104 games.

Koss was named to the Red Sox' 2022 spring training roster as a non-roster invitee. He began the season in Double-A with the Portland Sea Dogs. For the year, he played 125 total games for Portland, batting .260 with 17 home runs and 84 RBI.

San Francisco Giants On March 27, 2024, Koss was traded to the San Francisco Giants organization. He split the year between the rookie-level Arizona Complex League Giants, Double-A Richmond Flying Squirrels, and Triple-A Sacramento River Cats. In 88 appearances for the three affiliates, Koss batted a combined .299/.376/.496 with nine home runs, 47 RBI, and 13 stolen bases.

On March 26, 2025, the Giants selected Koss' contract after he made the team's Opening Day roster. On April 22, he made his first career pitching appearance, recording a scoreless inning of relief during an 11–3 blowout loss to the Milwaukee Brewers. On April 27, Koss recorded his first MLB run batted in with a single off of Texas Rangers reliever Jacob Latz, which scored Heliot Ramos. On May 13, Koss hit a go-ahead grand slam in the second inning of a game against the Arizona Diamondbacks. The hit, off of Brandon Pfaadt, was Koss' first career home run.

On June 2, 2026, Koss was diagnosed with a broken left wrist.

Personal life Koss and his wife, Lauren, have one daughter.