Hank Aaron has hit the most career home runs by a player younger than 40, with 713 home runs.

Interpreted as:

most homerun before turning 40 years old by a player

	NAME	HR	G	AB	R	H	2B	3B	RBI	BB	HBP	SO	SB	CS	PA	TB	XBH	SH	SF	IBB	GIDP	AVG	OBP	SLG	OPS
1	Hank Aaron H. Aaron	713	2,964	11,288	2,061	3,509	584	96	2,133	1,259	31	1,263	239	71	12,708	6,424	1,393	19	111	283	301	.311	.378	.569	.947
2	Babe Ruth B. Ruth	708	2,476	8,328	2,160	2,860	506	136	2,201	2,042	44	1,307	123		10,530	5,762	1,350	116				.343	.475	.692	1.167
3	Barry Bonds B. Bonds	683	2,654	8,942	2,016	2,674	551	74	1,797	2,210	88	1,408	503	140	11,329	5,422	1,308	4	85	562	142	.299	.439	.606	1.045
4	Alex Rodriguez A. Rodriguez	677	2,658	10,139	1,974	3,028	532	31	2,027	1,288	175	2,157	323	76	11,725	5,653	1,240	16	107	94	248	.299	.384	.558	.941
5	Albert Pujols A. Pujols	656	2,823	10,687	1,828	3,202	661	16	2,075	1,322	107	1,279	114	41	12,231	5,863	1,333	1	114	311	395	.300	.379	.549	.927
6	Willie Mays W. Mays	633	2,724	10,087	1,936	3,093	484	135	1,814	1,284	40	1,324	313	94	11,506	5,746	1,252	7	88	177	232	.307	.384	.570	.954
7	Ken Griffey Jr. K. Griffey Jr.	630	2,638	9,703	1,656	2,763	522	38	1,829	1,303	81	1,762	184	69	11,196	5,251	1,190	8	101	246	196	.285	.371	.541	.912
8	Sammy Sosa S. Sosa	609	2,354	8,813	1,475	2,408	379	45	1,667	929	59	2,306	234	107	9,896	4,704	1,033	17	78	154	202	.273	.344	.534	.878
9	Mark McGwire M. McGwire	583	1,874	6,187	1,167	1,626	252	6	1,414	1,317	75	1,596	12	8	7,660	3,639	841	3	78	150	147	.263	.394	.588	.982
10	Frank Robinson F. Robinson	583	2,770	9,936	1,825	2,928	528	72	1,802	1,407	198	1,518	203	79	11,659	5,349	1,183	17	101	218	276	.295	.389	.538	.928
11	Jim Thome J. Thome	582	2,373	7,934	1,520	2,199	427	26	1,610	1,666	67	2,386	19	20	9,741	4,424	1,035	1	73	165	152	.277	.404	.558	.961
12	Harmon Killebrew H. Killebrew	573	2,435	8,147	1,282	2,086	290	24	1,583	1,561	48	1,704	19	20	9,833	4,143	887	0	77	161	243	.256	.376	.509	.884
13	Manny Ramirez M. Ramirez	555	2,302	8,244	1,544	2,574	547	20	1,831	1,329	109	1,813	38	33	9,774	4,826	1,122	2	90	216	243	.312	.411	.585	.996
14	Rafael Palmeiro R. Palmeiro	549	2,710	10,060	1,612	2,913	569	38	1,769	1,309	85	1,295	95	40	11,580	5,205	1,156	15	111	168	223	.290	.372	.517	.890
15	Mike Schmidt M. Schmidt	548	2,404	8,352	1,506	2,234	408	59	1,595	1,507	79	1,883	174	91	10,062	4,404	1,015	16	108	201	156	.267	.380	.527	.908
16	Reggie Jackson R. Jackson	537	2,601	9,202	1,462	2,439	441	46	1,618	1,267	90	2,412	225	113	10,637	4,583	1,024	13	65	154	168	.265	.357	.498	.855
17	Mickey Mantle M. Mantle	536	2,401	8,101	1,675	2,415	344	72	1,509	1,733	12	1,718	152	42	9,907	4,511	952	14	47	126	113	.298	.420	.557	.977
18	Jimmie Foxx J. Foxx	534	2,317	8,134	1,751	2,645	458	125	1,924	1,457	13	1,311	87		9,676	4,955	1,117	72			70	.325	.428	.609	1.038
19	Frank Thomas F. Thomas	520	2,294	8,102	1,486	2,447	492	12	1,701	1,654	86	1,372	32	23	9,963	4,523	1,024	0	121	168	222	.302	.420	.558	.979
20	Eddie Mathews E. Mathews	512	2,391	8,537	1,509	2,315	354	72	1,454	1,443	26	1,490	69	41	10,100	4,349	938	36	58	107	127	.271	.376	.509	.885
21	Mel Ott M. Ott	511	2,730	9,455	1,859	2,876	488	72	1,865	1,720	64	895	89		11,348	5,041	1,071	109			38	.304	.415	.533	.948
22	Ernie Banks E. Banks	509	2,489	9,337	1,302	2,568	405	90	1,630	757	70	1,220	49	54	10,302	4,680	1,004	42	96	196	230	.275	.331	.501	.832
23	Miguel Cabrera M. Cabrera	507	2,708	10,052	1,530	3,095	610	17	1,850	1,229	72	2,039	40	21	11,458	5,260	1,134	5	100	238	355	.308	.384	.523	.907
24	David Ortiz D. Ortiz	503	2,257	8,103	1,340	2,303	584	18	1,641	1,239	36	1,664	15	9	9,465	4,432	1,105	2	85	194	214	.284	.378	.547	.925
25	Gary Sheffield G. Sheffield	499	2,476	8,949	1,592	2,615	454	25	1,633	1,435	133	1,125	251	103	10,635	4,616	978	9	109	127	225	.292	.394	.516	.909