Dennis O'Neill was a professional baseball player born in 1866, who had a brief career in the Major Leagues during the 1893 season. His time in the league spanned from June 18 to July 26, 1893, during an era marked by the transition toward modern baseball, as the sport was beginning to evolve from the deadball era into a more offensive-oriented game. O'Neill played a total of 7 games, primarily contributing as a position player.
In those limited appearances, O'Neill recorded 3 hits, with a batting average of .12, reflecting the challenges many players faced during this period of competitive baseball. Although he did not hit any home runs, he managed to drive in 2 runs and showcased his speed on the bases with 3 stolen bases. Despite his short stint in the Major Leagues, O'Neill's involvement in the early days of professional baseball places him among the ranks of players who contributed to the game's rich history. His career, while not extensively documented, serves as a reminder of the many individuals who helped shape the sport during its formative years.