The following railways operate in the Canadian province of Ontario.
Common freight carriers
Barrie Collingwood Railway (BCRY) Canadian National Railway (CN) including subsidiaries Algoma Central Railway (AC), Grand Trunk Western Railroad (GTW), and Sault Ste. Marie Bridge Company (SSAM), and lessor Arnprior–Nepean Railway Canadian Pacific Railway (CP) CSX Transportation (CSXT) Essex Terminal Railway (ETL) Goderich–Exeter Railway (GEXR) Huron Central Railway (HCRY) Minnesota, Dakota and Western Railway (MDW) Norfolk Southern Railway (NS) Ontario Northland Railway (ONT) including subsidiary Nipissing Central Railway Ontario Southland Railway (OS) Ottawa Valley Railway (RLK) Southern Ontario Railway (RLHH) Trillium Railway (TRRY) through subsidiaries Port Colborne Harbour Railway and St. Thomas and Eastern Railway
Passenger carriers
Amtrak (AMTK) Capital Railway Falls Incline Railway Port Stanley Terminal Rail South Simcoe Railway Via Rail (Via) Waterloo Central Railway York–Durham Heritage Railway Algoma Central Railway (CN) Polar Bear Express (ONTC)
Light Rail Transit
Ion rapid transit
OC Transpo
Toronto Transit Commission
Defunct railways
Electric
Belleville Traction Company
Berlin and Bridgeport Electric Street Railway
Berlin and Northern Railway
Berlin and Waterloo Street Railway
Brantford and Hamilton Electric Railway
Brantford Street Railway
Buffalo Railway
Canadian National Electric Railways
Chatham, Wallaceburg and Lake Erie Railway
City Railway of Windsor
City and Suburban Electric Railway
Cornwall Electric Street Railway
Cornwall Street Railway, Light and Power Company
Davenport Street Railway
Fort William Electric Railway
Galt and Preston Street Railway
Galt, Preston and Hespeler Street Railway
Grand River Railway (GRNR) Grand Valley Railway Guelph Railway Guelph Radial Railway Hamilton Cataract Power, Light and Traction Company Hamilton and Dundas Street Railway Hamilton Electric Light and Cataract Power Company Hamilton, Grimsby and Beamsville Electric Railway Hamilton Radial Electric Railway Hamilton Street Railway Hamilton, Waterloo and Guelph Railway Huron, Bruce and Grey Electric Railway Huron and Ontario Electric Railway (c. 1906 planned and never built) Hydro-Electric Railways International Railway International Transit Company Kingston, Portsmouth and Cataraqui Electric Railway Kingston Street Railway Kitchener and Waterloo Street Railway Lake Erie and Northern Railway (LEN) Leander Colt Incline London and Lake Erie Railway and Transportation Company London and Port Stanley Railway (LPS) London Street Railway Maid of the Mist Incline Metropolitan Street Railway Metropolitan Street Railway of Toronto Middlesex and Elgin Inter-urban Railway Mount McKay and Kakabeka Falls Railway Niagara Falls, Park and River Railway Niagara Falls, Wesley Park and Clifton Tramway Company Niagara, St. Catharines and Toronto Railway (NS&T) Niagara, Welland and Lake Erie Railway Nipissing Central Railway North Yonge Railways Ontario Southern Railway Ontario Traction Company Ontario West Shore Railway Ontario West Shore Electric Railway Oshawa Railway Ottawa City Passenger Railway Ottawa Electric Railway Ottawa Electric Street Railway Peterboro and Ashburnham Street Railway Peterboro Radial Railway Port Arthur Civic Company Port Arthur Electric Street Railway Port Arthur and Fort William Electric Railway Port Dalhousie, St. Catharines and Thorold Electric Street Railway Port Dover, Brantford, Berlin and Goderich Railway Preston and Berlin Railway St. Catharines, Merritton and Thorold Railway St. Catharines and Niagara Central Railway St. Catharines Street Railway St. Thomas Street Railway Sandwich, Windsor and Amherstburg Railway Sandwich and Windsor Passenger Railway Sarnia Street Railway Schomberg and Aurora Railway South Essex Electric Railway Southwestern Traction Company Sudbury and Copper Cliff Suburban Electric Railway Toronto Railway Toronto and Mimico Railway Toronto and Mimico Electric Railway and Light Company Toronto and Scarboro' Electric Railway, Light and Power Company Toronto Street Railway Toronto Suburban Railway Toronto Suburban Street Railway Toronto and York Radial Railway Weston, High Park and Toronto Street Railway Whirlpool Rapids Incline Windsor, Essex and Lake Shore Rapid Railway (WE&L) Windsor and Tecumseh Electric Railway Woodstock, Thames Valley and Ingersoll Electric Railway