| Competition: | Primera División |
| Season: | 1905 |
| Winners: | Alumni (5th title) |
| Promoted: | Reformer |
| Relegated: | (none) |
| Matches: | 43 |
| League Topscorer: | Tristán González (Estudiantes BA) Carlos Lett (Alumni) (12 goals each) |
| Biggest Home Win: | Alumni 14–0 Reformer |
| Biggest Away Win: | Barracas A.C. 1–12 Reformer |
| Prevseason: | 1904 |
| Nextseason: | 1906 |
The 1905 Argentine Primera División was the 14th season of top-flight football in Argentina. The season began on May 7 and ended on September 24[1] The 1905 championship was expanded to include 7 teams, who played in a league format, with each team playing the other twice.[1]
Alumni was the champion, winning its 5th league title in six seasons. The squad won the tournament after a 1–1 draw v. Estudiantes de Buenos Aires, one fixture before the end of the season. The line-up for that match was: José Buruca Laforia; Carlos Carr Brown, Jorge Gibson Brown; Andrés Mack, Patricio Barron Browne, Ernesto Brown; Gottlob Eduardo Weiss, Juan J. Moore, Alfredo Brown, Eliseo Brown, Eugenio Moore.
A new team, Reformer, from the city of Campana, registered to play the tournament. The team made a poor campaign, finishing the season with 60 goals conceded in 12 matches played.