{{Infoboks_tennisturnering
| titel                 = US National Championships 1891
| billede               = Mabel cahill and fellowes morgan.jpg
| billedtekst           = Vinderne af damedoublemesterskabet,<br/>[[Mabel Cahill]] og [[Emma Leavitt Morgan]]
| pixels                = 250
| alt                   = Mabel Cahill og Emma Leavitt Morgan
| arrangør              = [[United States National Lawn Tennis Association|United States<br/>National Lawn Tennis Association]]
| turneringsnummer      = 11
| dato                  = [[18. august|18.]] - [[26. august]] [[1891]] (mænd)<br/>[[22. juni|22.]] - [[28. juni]] [[1891]] (kvinder)
| spillested            = [[Newport Casino|Newport Casino Lawn Tennis Club]] (mænd)<br/>[[Philadelphia Cricket Club]] (kvinder)
| værtsby               = [[Newport (Rhode Island)|Newport]], [[Rhode Island]], [[USA]] (mænd)<br/>[[Philadelphia]], [[Pennsylvania]], [[USA]] (kvinder)
| underlag              = [[Græs]]
| kategori              = Nationalt mesterskab
| præmiesum             = 
| herresingle           = {{flagikon|USA|1877|size=18px}} [[Oliver Campbell]]
| herresingle_titel_nr  = 2
| damesingle            = {{flagikon|IRE|1783|size=18px}} [[Mabel Cahill]]
| damesingle_titel_nr   = 1
| herredouble           = {{flagikon|USA|1877|size=18px}} [[Oliver Campbell]]<br />{{flagikon|USA|1877|size=18px}} [[Bob Huntington]]
| herredouble_titel_nr  = 1
| damedouble            = {{flagikon|IRE|1783|size=18px}} [[Mabel Cahill]]<br />{{flagikon|USA|1877|size=18px}} [[Emma Leavitt Morgan]]
| damedouble_titel_nr   = 1
| forrige               = [[US National Championships 1890|1890]]
| næste                 = [[US National Championships 1892|1892]]
}}
'''US National Championships 1891''' var den 11. udgave af [[US Open (tennis)|US National Championships]] i [[tennis]] (nu [[US Open (tennis)|US Open]]), og herreturneringerne blev afholdt i [[Newport Casino|Newport Casino Lawn Tennis Club]] i [[Newport (Rhode Island)|Newport]], [[Rhode Island]], [[USA]] i perioden [[18. august|18.]] - [[26. august]] [[1891]], mens damerne spillede i [[Philadelphia Cricket Club]] i [[Philadelphia]], [[Pennsylvania]] i perioden [[22. juni|22.]] - [[28. juni]] [[1891]].
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