GNR Class O1

{{about|a class of 2-8-0 steam locomotives of the Great Northern Railway (United Kingdom) introduced in 1913|the class of 2-8-2 steam locomotives of the Great Northern Railway (United States) introduced in 1911|Great Northern O-1}}

{{Use dmy dates|date=April 2017}}

{{Use British English|date=April 2017}}

{{Infobox locomotive

| name = GNR O1 class
LNER O1 (later O3) Class

| image = Immingham Locomotive Depot geograph-2463746-by-Ben-Brooksbank.jpg

| alt =

| caption = No. 3491 at Immingham Locomotive Depot 1947

| powertype = Steam

| designer = Nigel Gresley

| builder = {{ubl|Doncaster Works (5)|North British Locomotive Co. (15)}}

| ordernumber =

| serialnumber =

| buildmodel =

| builddate = 1913–1919

| totalproduction = 20

| whytetype = 2-8-0

| uicclass = 1′D h2

| driver =

| gauge = {{track gauge|ussg}}

| leadingdiameter = {{convert|3|ft|2|in|mm|0|abbr=on}}

| driverdiameter =

| coupleddiameter = {{convert|4|ft|8|in|mm|0|abbr=on}}

| trailingdiameter =

| tenderdiameter =

| minimumcurve =

| wheelbase =

| engine total =

| leading =

| drivers =

| coupled =

| trailing =

| tender total =

| tendertruck =

| tenderbogie =

| pivotcentres =

| wheelspacing =

| length = {{convert|60|ft|11.5|in|m|abbr=on}}

| over couplers =

| over bufferbeams=

| width =

| height =

| frametype =

| axleload =

| leadingbogie/pony=

| coupled all =

| coupled 1 =

| coupled 2 =

| coupled 3 =

| coupled 4 =

| coupled 5 =

| coupled 6 =

| coupled 7 =

| coupled 8 =

| trail bogie/pony=

| tenderbogieload =

| tenderaxle =

| weightondrivers =

| locoweight = {{convert|76.2|-|78.65|LT|abbr=on}}

| tenderweight =

| locotenderweight =

| tendertype =

| fueltype = Coal

| fuelcap =

| watercap =

| tendercap =

| sandcap =

| fireboxtype =

| firearea = {{convert|27|sqft|m2|abbr=on}}

| boiler =

| boilertype =

| pitch =

| diameterinside = {{convert|5|ft|6|in|mm|abbr=on}}

| lengthinside =

| smalltubediameter=

| largetubediameter=

| boilerpressure = {{convert|180|lbf/in2|MPa|2|abbr=on}}

| safetyvalvetype =

| feedwaterheater =

| totalsurface = {{convert|2084|sqft|m2|abbr=on}}

| tubearea =

| fluearea =

| tubesandflues =

| fireboxarea = {{convert|162|sqft|m2|abbr=on}}

| superheatertype = 24

| superheaterarea = {{convert|570|sqft|m2|abbr=on}}

| cylindercount = Two, outside

| cylindersize = {{convert|21|x|28|in|mm|0|abbr=on}}

| valvegear = Walschaerts

| valvetype = {{convert|10|in|mm|0|adj=on}} piston valves

| valvetravel =

| valvelap =

| valvelead =

| transmission =

| trainheating =

| locobrakes =

| locobrakeforce =

| trainbrakes =

| safety =

| coupling =

| maxspeed =

| poweroutput =

| tractiveeffort = {{convert|33735|lbf|kN|2|abbr=on}}

| factorofadhesion =

| operator = {{ubl|Great Northern Railway (Great Britain)|London and North Eastern Railway|British Railways}}

| operatorclass =

| powerclass = 8F

| numinclass =

| fleetnumbers =

| officialname =

| axleloadclass = Route availability 6

| locale =

| deliverydate =

| firstrundate =

| lastrundate =

|nicknames=Tangos

| withdrawndate = 1947–1952

| scrapdate =

| disposition = All scrapped

| notes =

}}

The Great Northern Railway (GNR) Class O1 was a class of two-cylinder 2-8-0 steam locomotive designed by Nigel Gresley for heavy freight work and built by the GNR between 1913 and 1919.