The 1890 New York Giants season was the franchise's eighth season. The team finished in sixth place in the National League with a 63–68 record, 24 games behind the Brooklyn Bridegrooms. They also had to contend with a new crosstown rival, the New York Giants of the Players' League.

The 1890 Brooklyn Bridegrooms left the American Association and joined the National League. They won the league championship, becoming one of a select few teams to win championships in different leagues in back-to-back seasons.