Defending champion Oliver Campbell defeated Clarence Hobart in the challenge round, 2–6, 7–5, 7–9, 6–1, 6–2 to win the men's singles tennis title at the 1891 U.S. National Championships.

	Challenge round
	O Campbell		2	7	7	6	6
	C Hobart		6	5	9	1	2

	Semifinals									Finals
	C Hobart		6	6	6
	VG Hall		2	4	2
										C Hobart		6	3	6	6	6
										F Hovey		4	6	4	8	0
	F Hovey		6	6	3	1	6
	M Smith		4	2	6	6	4

	First round									Second round									Third round									Quarterfinals
	H Colby		6	4	6	6
	EK Rowland		1	6	1	1				H Colby		1	11	6	3	6
	FLV Hoppin		w/	o						FLV Hoppin		6	9	4	6	3
	FJ Bentley																		H Colby		0	6	0	4
	EL Hall		6	6	2	6													EL Hall		6	3	6	6
	M Fielding		2	3	6	4				EL Hall		5	7	6	6
	S McCormick		5	7	6	6				S McCormick		7	5	1	2
	W Hoopes		7	5	1	2																						EL Hall		6	4	9	4
	WV Johnson		6	6	6																							C Hobart		3	6	11	6
	S Woodward		2	2	2					WV Johnson		1	4	3
	C Hobart		8	6	6					C Hobart		6	6	6
	TP Borden		6	3	3														C Hobart		w/	o
	C Bunting		6	6	4	7	6												J Ryerson
	JA Hovey		4	8	6	5	4			C Bunting		1	2	4
	J Ryerson		6	6	6					J Ryerson		6	6	6
	ML Pratt		2	3	3

	First round									Second round									Third round									Quarterfinals
	CT Lee		6	6	6
	H Satterlee		0	1	1					CT Lee		6	6	6
	WP Jenks		6	6	9					WP Jenks		1	1	2
	JF Turrill		0	0	7														CT Lee		6	6	6
	E Colby		11	4	6	7													W Larned		2	2	4
	BJ Carroll		9	6	3	5				E Colby		1	1	1
	W Larned		8	6	8					W Larned		6	6	6
	H McCormick		6	4	6																							CT Lee		4	4	6	0
	VG Hall		6	6	6																							VG Hall		6	6	0	6
	FM Pile		1	1	1					VG Hall		2	6	6	6
	R Stevens		2	6	4	6	6			R Stevens		6	2	4	1
	B Lamb		6	3	6	2	1												VG Hall		6	2	6	6
	ST Chase		6	6	6														ST Chase		4	6	2	3
	G Herrick		2	2	1					ST Chase		3	6	6	6
	B Huntington		w/	o						B Huntington		6	4	3	3
	R Johnson

	First round									Second round									Third round									Quarterfinals
	F Hovey		6	6	6
	LR Parker		1	3	1					F Hovey		6	6	2	6
	HG Bixby		6	6	6					HG Bixby		3	4	6	4
	J Nichols		4	4	1														F Hovey		5	3	6	13	6
	PS Sears		5	6	6	10													PS Sears		7	6	2	11	2
	D Miller		7	3	2	3				PS Sears		6	6	2	7
	W Orcutt		6	10	6					W Orcutt		4	3	6	5
	EW Gould		3	8	1																							F Hovey		4	6	6	2	6
	H.I. Wilcox		6	2	6	6																						AWS Post		6	4	3	6	0
	WK Fowler		4	6	3	4				H.I. Wilcox		6	6	6
	CR Budlong		3	6	6	6				CR Budlong		4	2	2
	ES Rushmore		6	4	3	2													H.I. Wilcox		6	2	3	1
	AWS Post		6	6	6														AWS Post		0	6	6	6
	GT Scott		3	3	2					AWS Post		6	6	4	6
	GF Fearing		6	6	6					GF Fearing		3	3	6	4
	CA Brown		0	1	1

	First round									Second round									Third round									Quarterfinals
	M Smith		7	6	6
	DW Candler		5	2	1					M Smith		6	6	6
	G Brown		6	6	8					G Brown		0	4	2
	BS de Garmendia		1	0	6														M Smith		6	6	6
	B O'Connor		6	7	8														B O'Connor		2	2	3
	GN Notion		0	5	6					B O'Connor		6	6	6
	PS Oscanyan		6	4	6	6				PS Oscanyan		3	2	1
	E Stille		2	6	4	3																						M Smith		6	6	6
	T Horton		6	6	6																							J Clark		1	0	4
	EA Thompson		2	2	2					T Horton		0	1	3
	J Clark		6	4	6	6				J Clark		6	6	6
	ES White		1	6	1	3													J Clark		6	6	6
	JHF Hunt		6	6	6														JHF Hunt		4	2	4
	AWS Post		3	4	1					JHF Hunt		w/	o
	A Empie Wright		w/	o						A Empie Wright
	WH Trotter

• Albiero, Alessandro; Carta, Andrea (2010). The Grand Slam Record Book Vol. 1. Monte Porzio Catone: Effepi Libri. p. 574. ISBN 978-88-6002-017-8.