USL League One
| Organizing body | United Soccer League |
|---|---|
| Founded | April 2, 2017 |
| First season | 2019 |
| Country | United States |
| Confederation | CONCACAF (North American Football Union) |
| Number of clubs | 17 |
| Level on pyramid | 3 |
| Domestic cup | U.S. Open Cup |
| League cup | USL Cup |
| Current champion(s) | One Knoxville SC (2025) |
| Current Players' Shield | One Knoxville SC (2025) |
| Most championships | Union Omaha (2 titles) |
| Most Players' Shields | Union Omaha (3 titles) |
| Top scorer | Emiliano Terzaghi (58) |
| Broadcaster(s) | |
| Website | uslleagueone.com |
| Current: 2026 season | |
USL League One (USL1) is a professional men's soccer league in the United States that had its inaugural season in 2019. The Division 3 league is operated by the United Soccer League, the same group that operates the men's Division 2 USL Championship, women's Division 1 league USL Super League, and other leagues. As of 2026, the league has 17 active teams that are scheduled to play 32 regular-season games, followed by playoffs. All teams also participate in the USL Cup, adding four games, followed by knockout rounds.