NER Class R

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

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

{{one source|date=December 2016}}

{{Infobox locomotive

|powertype=Steam

|name = NER Class R
LNER Class D20

|image = Gateshead Locomotive Depot geograph-2327896-by-Ben-Brooksbank.jpg

|caption = 1907-built class R 2387, at Gateshead in 1954

|designer = Wilson Worsdell

|boiler = {{convert|4|ft|9|in|abbr=on}} diameter

|builder = NER Gateshead

|builddate = 1899-1907

|totalproduction = 60

|whytetype = 4-4-0

|gauge = {{Track gauge|uksg|allk=on}}

|leadingdiameter = {{convert|4|ft|0|in|3|abbr=on}}

|driverdiameter = {{convert|6|ft|10|in|3|abbr=on}}

|length =

|wheelbase = {{convert|23|ft|9|in|abbr=on}} engine
{{convert|12|ft|8|in|abbr=on}} tender
{{convert|45|ft|10+3/4|in|abbr=on}} total

|locoweight = D20/1: {{convert|54.1|LT|t ST|abbr=on}}
D20/2: {{convert|55.45|LT|t ST|abbr=on}}

|tenderweight = {{convert|41.2|LT|t ST|abbr=on}}

|locotenderweight = D20/1: {{convert|95.3|LT|abbr=on}}
D20/1: {{convert|96.65|LT|t ST|abbr=on}}

|axleload = {{convert|19.8|LT|t ST|abbr=on}}

|fueltype = Coal

|fuelcap =

|watercap =

|cylindercount = two inside

|cylindersize = {{convert|19|x|26|in|0|abbr=on}}

|boilerpressure = {{convert|200|psi|MPa|abbr=on}}
later reduced to {{convert|160|psi|MPa|abbr=on}}

|totalsurface = {{convert|1318.7|sqft|abbr=on}}

|firearea = {{convert|20|sqft|abbr=on}}

|fireboxarea = {{convert|139|sqft|abbr=on}}

|tubearea = {{convert|638.7|sqft|abbr=on}}

|fluearea = {{convert|292|sqft|abbr=on}}

|superheaterarea = {{convert|204|sqft|abbr=on}}

|tractiveeffort = {{convert|17025|lbf|kN|abbr=on}}
later reduced to {{convert|15567|lbf|kN|abbr=on}}

|valvegear = Stephenson

|operator = North Eastern Railway, London and North Eastern Railway, British Railways

|powerclass = BR: 2P

|operatorclass=

|retiredate = 1943-1957

|disposition = All scrapped

}}

The NER Class R (later, LNER Class D20) was a class of 4-4-0 steam locomotive, designed by Wilson Worsdell for the North Eastern Railway. They passed to the London and North Eastern Railway (LNER) in 1923. In 1936, some were rebuilt with long-travel piston valves and classified D20/2. The unrebuilt locomotives were re-classified D20/1.