Freddie Lindstrom has the most career triples by a player younger than 21, with 22 triples.

Interpreted as:

most triples before turning 21 years old by a player

	NAME	3B	G	AB	R	H	2B	HR	RBI	BB	HBP	SO	SB	CS	PA	TB	XBH	SH	SF	IBB	GIDP	AVG	OBP	SLG	OPS
1	Freddie Lindstrom F. Lindstrom	22	297	977	152	286	37	13	113	67	5	51	19		1,085	406	72	36				.293	.341	.416	.757
2	Buddy Lewis B. Lewis	17	245	1,042	172	308	43	11	117	77	5	79	10		1,136	418	71	12				.296	.347	.401	.748
3	Phil Cavarretta P. Cavarretta	17	315	1,162	154	315	51	19	155	68	7	114	15		1,250	457	87	13				.271	.315	.393	.709
4	Rogers Hornsby R. Hornsby	17	170	597	75	182	19	9		47	4	69	17		663	262	45	15				.305	.360	.439	.798
5	Jimmie Foxx J. Foxx	16	215	571	118	189	38	16	105	76	2	61	6		664	307	70	15				.331	.411	.538	.949
6	Travis Jackson T. Jackson	15	250	932	127	270	38	15	113	42	0	98	9		992	383	68	18				.290	.320	.411	.731
7	Whitey Witt W. Witt	13	137	536	59	129	14	2		54	2	68	17		598	175	29	6				.241	.313	.326	.639
8	Stuffy McInnis S. McInnis	13	176	561	84	175	23	4		29	5		22		617	236	40	22				.312	.351	.421	.772
9	Richard Hoblitzell R. Hoblitzell	13	174	633	67	188	26	4		49	4		20		717	252	43	31				.297	.351	.398	.749
10	Bryce Harper B. Harper	12	257	957	169	260	50	42	117	117	7	214	29	10	1,094	460	104	6	7	4	12	.272	.353	.481	.834
11	Mickey Mantle M. Mantle	12	238	890	155	262	48	36	152	118	0	185	12	8	1,012	442	96	4			8	.294	.377	.497	.874
12	Al Kaline A. Kaline	11	320	1,120	173	346	42	32	147	105	6	106	16	13	1,246	506	85	7	8	12	36	.309	.369	.452	.821
13	Ruben Sierra R. Sierra	10	113	382	50	101	13	16	55	22	1	65	7	8	411	182	39	1	5	3	8	.264	.302	.476	.779
14	Robin Yount R. Yount	10	398	1,469	171	383	59	13	129	83	2	178	34	21	1,590	501	82	23	13	6	25	.261	.299	.341	.640
15	Cesar Cedeno C. Cedeno	10	251	966	131	271	61	17	123	40	5	159	37	13	1,026	403	88	6	9	7	17	.281	.310	.417	.727
16	Ed Kranepool E. Kranepool	10	361	1,224	113	299	56	22	112	89	4	172	5	8	1,336	441	88	5	14	9	33	.244	.295	.360	.655
17	Ken Hubbs K. Hubbs	10	170	690	94	177	25	6	51	35	3	137	3	7	744	240	41	13	3	0	20	.257	.294	.348	.642
18	Arky Vaughan A. Vaughan	10	129	497	71	158	15	4	61	39	6	26	10		555	205	29	13				.318	.375	.412	.787
19	Claudell Washington C. Washington	9	195	704	83	212	31	8	83	38	5	104	44	21	757	285	48	2	8	7	16	.301	.338	.405	.743
20	Ted Williams T. Williams	9	119	463	92	145	35	21	117	74	0	52	2		538	261	65	1			9	.313	.408	.564	.972
21	Mel Ott M. Ott	9	391	1,203	237	388	72	61	253	180	8	92	12		1,416	661	142	25				.323	.414	.549	.964
22	Roberto Clemente R. Clemente	8	102	405	40	101	17	4	39	17	2	57	2	2	430	146	29	3	3	3	11	.249	.281	.360	.642
23	Sibby Sisti S. Sisti	8	261	959	130	242	39	8	76	70	5	140	12		1,049	321	55	15			12	.252	.307	.335	.641
24	Bobby Doerr B. Doerr	8	200	656	92	180	31	7	94	76	1	64	7		759	248	46	26				.274	.351	.378	.729
25	Rougned Odor R. Odor	7	114	386	39	100	14	9	48	17	5	71	4	7	417	155	30	6	3	1	7	.259	.297	.402	.698