Nate Colbert and Stan Musial are tied for the most homers in a day, with 5 home runs.

Interpreted as:

most MLB home runs by a player in a day

	NAME	HR	DAY	AB	R	H	2B	3B	RBI	BB	HBP	SO	SB	CS	PA	TB	XBH	SH	SF	IBB	GIDP	AVG	OBP	SLG	OPS
1	Nate Colbert N. Colbert	5	8/1/1972	9	7	7	0	0	13	1	0	1	0	0	10	22	5	0	0	0	0	.778	.800	2.444	3.244
2	Stan Musial S. Musial	5	5/2/1954	8	6	6	0	0	9	2	0	0	0	0	10	21	5	0	0		0	.750	.800	2.625	3.425
3	Eugenio Suárez E. Suárez	4	4/26/2025	4	4	4	0	0	5	0	0	0	0	0	4	16	4	0	0	0	0	1.000	1.000	4.000	5.000
4	J.D. Martinez	4	9/4/2017	5	4	4	0	0	6	0	0	1	0	0	5	16	4	0	0	0	0	.800	.800	3.200	4.000
5	Scooter Gennett S. Gennett	4	6/6/2017	5	4	5	0	0	10	0	0	0	0	0	5	17	4	0	0	0	0	1.000	1.000	3.400	4.400
6	Josh Hamilton J. Hamilton	4	5/8/2012	5	4	5	1	0	8	0	0	0	0	0	5	18	5	0	0	0	0	1.000	1.000	3.600	4.600
7	Carlos Delgado C. Delgado	4	9/25/2003	4	4	4	0	0	6	0	0	0	0	0	4	16	4	0	0	0	0	1.000	1.000	4.000	5.000
8	Shawn Green S. Green	4	5/23/2002	6	6	6	1	0	7	0	0	0	0	0	6	19	5	0	0	0	0	1.000	1.000	3.167	4.167
9	Mike Cameron M. Cameron	4	5/2/2002	5	4	4	0	0	4	0	1	0	0	0	6	16	4	0	0	0	0	.800	.833	3.200	4.033
10	Mark Whiten M. Whiten	4	9/7/1993	9	5	4	0	0	13	1	0	1	0	0	10	16	4	0	0	0	0	.444	.500	1.778	2.278
11	Bob Horner B. Horner	4	7/6/1986	5	4	4	0	0	6	0	0	0	0	0	5	16	4	0	0	0	0	.800	.800	3.200	4.000
12	Jason Thompson J. Thompson	4	6/26/1984	10	4	4	0	0	5	0	0	1	0	0	10	16	4	0	0	0	0	.400	.400	1.600	2.000
13	Al Oliver A. Oliver	4	8/17/1980	9	6	6	1	1	7	1	0	0	0	0	10	21	6	0	0	1	0	.667	.700	2.333	3.033
14	Otto Velez O. Velez	4	5/4/1980	9	4	4	0	0	10	0	0	2	0	0	9	16	4	0	0	0	0	.444	.444	1.778	2.222
15	Mike Schmidt M. Schmidt	4	4/17/1976	6	4	5	0	0	8	0	0	0	0	0	6	17	4	0	0	0	0	.833	.833	2.833	3.667
16	Graig Nettles G. Nettles	4	4/14/1974	10	4	5	0	0	7	0	0	2	0	0	10	17	4	0	0	0	0	.500	.500	1.700	2.200
17	Rusty Staub R. Staub	4	8/1/1970	8	6	5	0	0	6	1	0	1	0	0	9	17	4	0	0	0	0	.625	.667	2.125	2.792
18	Bobby Murcer B. Murcer	4	6/24/1970	7	4	4	0	0	5	1	0	1	0	0	8	16	4	0	0	0	0	.571	.625	2.286	2.911
19	Lee May L. May	4	7/15/1969	6	4	4	0	0	10	2	0	1	0	0	8	16	4	0	0	0	0	.667	.750	2.667	3.417
20	Adolfo Phillips A. Phillips	4	6/11/1967	9	5	6	0	0	8	0	0	1	1	1	9	18	4	0	0	0	0	.667	.667	2.000	2.667
21	Leo Cardenas L. Cardenas	4	6/5/1966	8	4	6	1	0	8	0	0	0	0	0	8	19	5	0	0	0	0	.750	.750	2.375	3.125
22	Harmon Killebrew H. Killebrew	4	9/21/1963	9	4	4	0	0	6	0	0	1	0	0	9	16	4	0	0	0	1	.444	.444	1.778	2.222
23	Rocky Colavito R. Colavito	4	8/27/1961	9	4	4	0	0	7	0	0	2	0	0	9	16	4	0	0	0	0	.444	.444	1.778	2.222
24	Roger Maris R. Maris	4	7/25/1961	9	4	5	0	0	8	0	0	1	0	0	9	17	4	0	0	0	0	.556	.556	1.889	2.444
25	Willie Mays W. Mays	4	4/30/1961	5	4	4	0	0	8	0	0	0	0	0	5	16	4	0	0	0	0	.800	.800	3.200	4.000