Alex Rodriguez has hit the most career home runs by a player younger than 31, with 451 homers.

Interpreted as:

most homeruns by a player before age 31

	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	Alex Rodriguez A. Rodriguez	451	1,689	6,563	1,317	2,004	353	26	1,299	786	104	1,355	235	60	7,531	3,762	830	16	62	56	150	.305	.385	.573	.958
2	Ken Griffey Jr. K. Griffey Jr.	438	1,680	6,352	1,163	1,883	342	33	1,270	841	56	1,101	173	64	7,319	3,605	813	6	64	187	116	.296	.380	.568	.948
3	Jimmie Foxx J. Foxx	429	1,710	6,116	1,355	2,048	346	102	1,522	1,106	9	935	76		7,293	3,885	877	62				.335	.437	.635	1.073
4	Albert Pujols A. Pujols	408	1,558	5,733	1,186	1,900	426	15	1,230	914	73	646	75	34	6,782	3,580	849	1	61	236	203	.331	.426	.624	1.050
5	Mickey Mantle M. Mantle	404	1,675	5,895	1,339	1,821	256	67	1,152	1,251	10	1,218	132	33	7,199	3,423	727	13	30	78	62	.309	.429	.581	1.010
6	Eddie Mathews E. Mathews	399	1,634	6,002	1,138	1,690	248	61	1,083	1,030	18	978	60	31	7,124	3,257	708	31	43	62	87	.282	.386	.543	.929
7	Andruw Jones A. Jones	369	1,781	6,472	1,053	1,693	333	35	1,120	727	83	1,417	138	55	7,350	3,203	737	6	62	65	162	.262	.341	.495	.836
8	Mel Ott M. Ott	369	1,864	6,544	1,332	2,061	359	63	1,389	1,140	38	566	62		7,808	3,653	791	86			5	.315	.419	.558	.978
9	Miguel Cabrera M. Cabrera	366	1,672	6,266	1,066	2,007	416	14	1,266	802	47	1,212	36	18	7,177	3,549	796	5	57	181	215	.320	.398	.566	.965
10	Frank Robinson F. Robinson	366	1,631	6,009	1,145	1,824	342	52	1,108	768	126	863	165	64	6,975	3,368	760	13	59	138	163	.304	.390	.560	.951
11	Hank Aaron H. Aaron	366	1,656	6,510	1,181	2,085	351	79	1,216	603	20	653	125	41	7,216	3,692	796	19	64	133	180	.320	.376	.567	.943
12	Juan Gonzalez J. Gonzalez	362	1,363	5,292	860	1,554	312	21	1,142	376	50	1,031	22	17	5,779	2,994	695	2	59	66	142	.294	.343	.566	.908
13	Harmon Killebrew H. Killebrew	358	1,341	4,631	786	1,220	166	14	911	797	35	1,024	6	10	5,500	2,488	538	0	37	63	113	.263	.373	.537	.910
14	Adam Dunn A. Dunn	354	1,448	4,975	865	1,246	266	10	880	990	71	1,632	59	21	6,065	2,594	630	2	27	107	75	.250	.381	.521	.902
15	Sammy Sosa S. Sosa	336	1,409	5,289	841	1,413	206	35	941	428	36	1,369	224	99	5,808	2,697	577	17	38	64	121	.267	.324	.510	.834
16	Mike Trout M. Trout	334	1,367	4,938	1,022	1,495	285	51	867	904	91	1,312	204	37	5,985	2,884	670	0	52	115	61	.303	.416	.584	1.000
17	Ralph Kiner R. Kiner	329	1,212	4,327	827	1,214	167	34	887	870	22	618	20	3	5,223	2,436	530	4			103	.281	.404	.563	.967
18	Willie Mays W. Mays	328	1,397	5,331	1,037	1,683	268	95	958	671	20	597	223	72	6,071	3,125	691	1	48	98	120	.316	.391	.586	.977
19	Manny Ramirez M. Ramirez	317	1,281	4,626	878	1,458	315	13	1,068	724	57	1,034	29	25	5,459	2,750	645	2	50	98	128	.315	.410	.594	1.005
20	Lou Gehrig L. Gehrig	316	1,438	5,344	1,261	1,831	378	126	1,352	938	23	563	78		6,407	3,409	820	102				.343	.443	.638	1.081
21	Duke Snider D. Snider	314	1,422	5,309	992	1,607	288	66	999	691	15	873	92	41	6,077	2,969	668	43	19	57	124	.303	.383	.559	.943
22	Giancarlo Stanton G. Stanton	312	1,185	4,329	698	1,160	246	11	796	584	46	1,402	42	15	4,989	2,364	569	0	30	80	95	.268	.359	.546	.905
23	Johnny Bench J. Bench	310	1,633	5,947	876	1,593	311	22	1,111	705	17	1,024	59	34	6,755	2,878	643	6	80	119	151	.268	.343	.484	.827
24	Babe Ruth B. Ruth	309	1,199	3,926	985	1,355	282	85	944	939	27	668	74		4,941	2,734	676	49				.345	.474	.696	1.171
25	Bryce Harper B. Harper	306	1,508	5,384	997	1,513	327	24	889	959	44	1,395	133	46	6,454	2,806	657	12	55	120	116	.281	.391	.521	.912