This is a list of railroad companies which currently or formerly operated at least partially in the U.S. state of Connecticut.

Active railroads

Freight carriers + Name Mark Image Founded Predecessor(s) Description Owner ReferenceBranford Steam RailroadBRFD1903N/AHauls stone from a Tilcon quarry in North Branford.Tilcon ConnecticutCentral New England RailroadCNZR1995Operates two branch lines in and around Hartford.IndependentConnecticut Southern RailroadCSO1996ConrailOperates along Amtrak's New Haven–Springfield Line via trackage rights, along with several branches. Hauls freight between Cedar Hill Yard and West Springfield, Massachusetts, for CSX.Genesee & WyomingCSX TransportationCSXT1980ConrailAssumed Conrail's Connecticut operations in 1999, chiefly on the New Haven Line and at Cedar Hill Yard.CSX CorporationHousatonic RailroadHRRC1983Operates a north-south line in western Connecticut, along with several branches.IndependentNaugatuck RailroadNAUG1996Guilford Rail SystemPrimarily a heritage railroad, but also provides freight service between Waterbury and Torrington.Railroad Museum of New EnglandNew England Central RailroadNECR1995Central Vermont RailwayOperates a main line between New London and the Massachusetts state line, via Willimantic.Genesee & WyomingPan Am SouthernPAS2009Pan Am RailwaysJoint venture between NS and PAR, operates all former PAR trackage in the state.Providence and Worcester RailroadPW1847 (original company)Penn Central Transportation CompanySeparated from Penn Central Transportation Company in 1973, operates across central and western Connecticut.Genesee & Wyoming

Passenger carriers

+NameMarkImageFoundedPredecessor(s)DescriptionOwnerReferencesAmtrakAMTK1971Penn Central Transportation CompanyNational intercity passenger railroad of the United States. Operates on the Northeast Corridor, owns and operates the New Haven–Springfield Line.Federal government of the United StatesCT RailCNDX1990N/ABrand for commuter rail services operated by the State of Connecticut. Includes the Hartford Line, run under contract by TransitAmerica Services and Alternate Concepts, and Shore Line East, run under contract by Amtrak.Connecticut Department of TransportationMetro-North RailroadMNCW1983ConrailOperates commuter service along the New Haven Line, New Canaan Branch, Danbury Branch, and Waterbury Branch, under contract with the state of Connecticut.Metropolitan Transportation Authority

Heritage railroads +NameMarkImageFoundedPredecessor(s)DescriptionOwnerReferencesConnecticut Trolley Museum1940 Hartford and Springfield Street Railway CompanyDanbury Railway MuseumDRMX1994Metro-North RailroadIndependentNaugatuck RailroadNAUG1996Railroad Museum of New EnglandShore Line Trolley Museum1945Connecticut CompanyBranford Electric Railway AssociationValley RailroadVALE1971Penn Central Transportation Company

Defunct railroads NameMarkSystemThis is one or more of the Class I railroads that the railroad became part of, if any.FromThis date refers to the year in which the railroad company was chartered or formed, and may be earlier than when the company ran its first train, if ever.ToThis date refers to when the railroad company formally ceased to exist. Many railroads were leased by other companies, de facto becoming part of them, but remained separate on paper for some time. If this date differs from when the railroad last operated independently, this will be noted in the description section.SuccessorDescriptionReferencesBoston, Hartford and Erie RailroadNH18631874New York and New England RailroadBoston and Maine CorporationBM1983Still exists as a lessor of Pan Am Railways operating subsidiary Springfield Terminal RailwayBoston and New York Air-Line RailroadNH18751907New York, New Haven and Hartford RailroadBoston and New York Central RailroadNH18531858Midland RailroadBoston, Norwich and New London RailroadNH18321836Norwich and Worcester RailroadBranch CompanyNH18451850Hartford and New Haven RailroadBuilt a short spur between the H&NH main line in Hartford, and the Connecticut River.Central New England RailwayCNENH18991927New York, New Haven and Hartford RailroadCentral New England and Western RailroadNH18891892Philadelphia, Reading and New England RailroadCentral Vermont RailroadCN18731899Central Vermont RailwayCentral Vermont RailwayCVCN18991995New England Central RailroadColchester RailroadNH18761907New York, New Haven and Hartford RailroadConnecticut Central RailroadNo relation to the identically named company which existed 1871-1887.CCCL19871998Providence and Worcester RailroadShortline railroad that operated former Conrail trackage in and around Middletown, Connecticut.Connecticut Central RailroadNH18711887New York and New England RailroadConnecticut Valley RailroadNH18681880Hartford and Connecticut Valley RailroadConnecticut Western RailroadNH18681881Hartford and Connecticut Western RailroadConsolidated Rail CorporationCR19761999CSX TransportationDanbury and Norwalk RailroadNH18501907New York, New Haven and Hartford RailroadDanbury Terminal RailroadDTRR19931996Housatonic RailroadEast Granby and Suffield RailroadNH19011908Central New England RailwayEast Thompson RailroadNH18531858Boston and New York Central RailroadFairfield County RailroadNH18351850Danbury and Norwalk RailroadFarmington Valley RailroadNH18521862New Haven and Northampton RailroadBuilt an extension of the New Haven and Northampton Railroad from Granby to the Massachusetts state line, leased by the NH&N soon after completion.Hartford and Connecticut Valley RailroadNH18791892New York, New Haven and Hartford RailroadHartford and Connecticut Western RailroadNH18811947New York, New Haven and Hartford RailroadHartford and New Haven RailroadNH18331872New York, New Haven and Hartford RailroadThe first railroad built in Connecticut; construction began in 1836. Opened from New Haven to Hartford in 1839, to Springfield, Massachusetts in 1844. Merged with the New York and New Haven Railroad in 1872.Hartford and Providence RailroadNH18471849Hartford, Providence and Fishkill RailroadHartford, Providence and Fishkill RailroadNH18491879New York and New England RailroadHartford and Springfield RailroadNH18351847Hartford and New Haven RailroadFormed in 1835 to build north from Hartford to the Massachusetts state line. Owned and operated by the Hartford and New Haven Railroad, merged into that company in 1847.Housatonic RailroadNH18361898New York, New Haven and Hartford RailroadManchester RailroadNH18331847Hartford and Providence RailroadManufacturers' RailroadKnown as the Manufacturers' Street Railway 1893-1897.NH18931907New York, New Haven and Hartford RailroadMeriden and Cromwell RailroadNH18821888Meriden, Waterbury and Connecticut River RailroadMeriden and Waterbury RailroadNH18871888Meriden, Waterbury and Connecticut River RailroadMeriden, Waterbury and Connecticut River RailroadNH18881896Middletown, Meriden and Waterbury RailroadMiddletown RailroadNH18441850Hartford and New Haven RailroadFormed by citizens of Middletown to connect their city to the H&NH main line in Berlin. Built in 1848, purchased by the H&NH in 1850.Middletown Extension RailroadNH18571861Hartford and New Haven RailroadFormed to build an extension of the Middletown Railroad to the Connecticut River. Built in 1860, consolidated into the Hartford and New Haven Railroad the following year.Middletown, Meriden and Waterbury RailroadNH18971907New York, New Haven and Hartford RailroadMidland RailroadNH18581862Midland Land Damage CompanyMidland Land Damage CompanyNH18611863Southern Midland RailroadNaugatuck RailroadNH18451906New York, New Haven and Hartford RailroadNew Britain and Middletown RailroadNH18521868Hartford and New Haven RailroadFormed by citizens in New Britain to construct a short branch to the H&NH in Berlin. Constructed in 1862, it was operated by the H&NH until that company absorbed it in 1868.New Canaan RailroadNH18661883Stamford and New Canaan RailroadNew England RailroadNH18951908New York, New Haven and Hartford RailroadNew Haven and Derby RailroadNH18641907New York, New Haven and Hartford RailroadNew Haven, Middletown and Willimantic RailroadNH18671875Boston and New York Air-Line RailroadNew Haven and New London RailroadNH18481865Shore Line RailwayNew Haven, New London and Stonington RailroadNH18581864New York, Providence and Boston RailroadNew Haven and Northampton RailroadNH18461910New York, New Haven and Hartford RailroadNew London Northern RailroadCN18591951Central Vermont RailwayNew London and Stonington RailroadNH18521864New York, Providence and Boston RailroadNew London, Willimantic and Palmer RailroadCN18491861New London Northern RailroadNew London, Willimantic and Springfield RailroadCN18471849New London, Willimantic and Palmer RailroadNew York and Boston RailroadNH18461865Boston, Hartford and Erie RailroadNew York and Hartford RailroadNH18451849Hartford, Providence and Fishkill RailroadNew York, Housatonic and Northern RailroadNH18641882Housatonic RailroadNew York and New England RailroadNH18731895New England RailroadNew York and New Haven RailroadNH18441872New York, New Haven and Hartford RailroadNew York, New Haven and Hartford RailroadNHNH18721969Penn Central Transportation CompanyNew York, Providence and Boston RailroadNH18331893New York, New Haven and Hartford RailroadNew York and Stonington RailroadNH18321833New York, Providence and Boston RailroadNorwich and Worcester RailroadNH18361976Consolidated Rail CorporationPenn Central Transportation CompanyPC19691976Consolidated Rail CorporationPhiladelphia, Reading and New England RailroadNH18921899Central New England RailwayRockville RailroadNH18631907New York, New Haven and Hartford RailroadRockville Branch RailroadNH18571863New York, New Haven and Hartford RailroadShepaug, Litchfield and Northern RailroadKnown as the Shepaug Valley railroad 1866–1873, Shepaug Railroad 1873-1887.NH18661898New York, New Haven and Hartford RailroadShore Line RailwayNH18641897New York, New Haven and Hartford RailroadSouth Manchester RailroadNH18661976Consolidated Rail CorporationSouthbridge and Blackstone RailroadNH18491853Boston and New York Central RailroadSouthern Midland RailroadNH18631863Boston, Hartford and Erie RailroadStamford and New Canaan RailroadNH18821890New York, New Haven and Hartford RailroadThompson and Willimantic RailroadNH18571863Boston, Hartford and Erie RailroadVermont Central RailroadCN18711873Central Vermont RailroadWatertown and Waterbury RailroadNH18691893Naugatuck RailroadChartered in 1869 to connect Watertown to the Naugatuck Railroad in Waterbury. Was leased by the Naugatuck Railroad upon opening in the fall of 1870, which absorbed it in 1893.Windsor Locks and Suffield RailroadNH18681871Hartford and New Haven RailroadFormed in 1868 to construct a branch between Suffield and Windsor Locks, where it met the H&NH. Built in 1870, it was absorbed by the H&NH in 1871.

Street railroads Entries in this list were interurbans, streetcars, or other electric railroads dedicated to passenger transport.