Oscar Emil "Happy" Felsch (August 22, 1891 – August 17, 1964) was an American center fielder in Major League Baseball who played for the Chicago White Sox from 1915 to 1920. He is probably best known for his involvement in the 1919 Black Sox scandal.

Felsch was born in Milwaukee, Wisconsin. He dropped out of school in the sixth grade and played baseball on Milwaukee sandlots. He began his professional baseball career in the Wisconsin-Illinois League in 1913. The next season, he batted .304 and slugged .512 for the American Association's Milwaukee Brewers, and was purchased by the White Sox.

From 1916 to 1920, Felsch was one of the best hitters in the American League, finishing in the top 10 in more than a few major batting categories. His 102 runs batted in was good enough for second place in 1917, as the White Sox won the American League pennant as well as the World Series. He missed most of the 1918 season due to military service.

Felsch continued his good hitting and fielding in 1919. He had a strong throwing arm and was highly regarded as a center fielder; he led the AL in outfield putouts and assists in 1919. The White Sox won the pennant going away.