The Trillium Railway (reporting mark TRRY) is a Canadian short-line railroad operating in the province of Ontario. Much of its right-of-way in the Niagara area was formerly part of the "Welland Canal Railway" (also known as the Welland Railway) that closely followed the route of the second Welland Canal.
Trillium Railway began operations in 1997 with only eleven kilometres of railway, all of which were located in Port Colborne.
With an expansion in 1998, Trillium added 55 kilometres of track between Delhi and St. Thomas. Another expansion in 1999 added another 55 kilometres of track in Welland, Thorold and St. Catharines.
In the Niagara Region, Trillium's trackage, referred to as Port Colborne Harbour Railway, is made up of Canadian National's former secondary and branch lines, including a number of urban spurs, on the west side of the Canal. CN and Canadian Pacific interchange with Trillium at CN/CP Feeder. Trillium no longer operates on the south tracks of the Townline Tunnel under the Welland Canal.
The St. Thomas and Eastern Railway operated over the former CN Cayuga Spur, the historical "Canada Air Line". It reached the city of St. Thomas via trackage rights over CN.