The 1899–1900 St Helens R.F.C. season was the club's fifth in the Northern Rugby Football Union, the 26th in their history. In their highest ever finish in a rugby league competition, and their most successful season, the club finished fourth in the Lancashire Senior Championship.[1] In the Challenge Cup, St Helens were beaten in the first round by rivals Warrington.[2] However, they did manage some silverware in the season, by beating league winners Runcorn 6-0 in the South Lancashire Cup final.[3]