The modern-era record for highest batting average for a season is held by Napoleon_Lajoie, who hit .426 in 1901, the first year of play for the American_League.
Here's the all-time list as of the start of the 2008 season:
SEASON
AVERAGE YEAR AVG
1 Hugh Duffy 1894 .440
2 Tip O'Neill 1887 .435
3 Ross Barnes 1876 .429
4 Nap Lajoie 1901 .426
5 Willie Keeler 1897 .424
6 Rogers Hornsby 1924 .424
7 George Sisler 1922 .420
8 Ty Cobb 1911 .420
9 Fred Dunlap 1884 .412
10 Ed Delahanty 1899 .410
11 Jesse Burkett 1896 .410
12 Jesse Burkett 1895 .409
13 Ty Cobb 1912 .409
14 Joe Jackson 1911 .408
15 Sam Thompson 1894 .407
16 George Sisler 1920 .407
17 Ed Delahanty 1894 .407
18 Ted Williams 1941 .406
19 Billy Hamilton 1894 .404
20 Ed Delahanty 1895 .404
21 Rogers Hornsby 1925 .403
22 Harry Heilmann 1923 .403
23 Pete Browning 1887 .402
24 Rogers Hornsby 1922 .401
25 Bill Terry 1930 .401
26 Hughie Jennings 1896 .401
27 Ty Cobb 1922 .401
28 Cap Anson 1881 .399
29 Lefty O'Doul 1929 .398
30 Harry Heilmann 1927 .398
31 Rogers Hornsby 1921 .397
32 Ed Delahanty 1896 .397
33 Jesse Burkett 1899 .396
34 Joe Jackson 1912 .395
35 Tony Gwynn 1994 .394
36 Harry Heilmann 1921 .394
37 Babe Ruth 1923 .393
38 Harry Heilmann 1925 .393
39 Babe Herman 1930 .393
40 Joe Kelley 1894 .393
41 Sam Thompson 1895 .392
42 John McGraw 1899 .391
43 Ty Cobb 1913 .390
44 Fred Clarke 1897 .390
45 Al Simmons 1931 .390
46 George Brett 1980 .390
47 Tris Speaker 1925 .389
48 Bill Lange 1895 .389
49 Billy Hamilton 1895 .389
50 Ty Cobb 1921 .389
51 Ted Williams 1957 .388
52 King Kelly 1886 .388
53 Rod Carew 1977 .388
54 Luke Appling 1936 .388
55 Tris Speaker 1920 .388
56 Deacon White 1877 .387
57 Rogers Hornsby 1928 .387
58 Tris Speaker 1916 .386
59 Willie Keeler 1896 .386
60 Chuck Klein 1930 .386
T61 Lave Cross 1894 .386
T61 Hughie Jennings 1895 .386
63 Willie Keeler 1898 .385
64 Arky Vaughan 1935 .385
65 Al Simmons 1925 .384
66 Rogers Hornsby 1923 .384
67 Ty Cobb 1919 .384
68 Nap Lajoie 1910 .384
69 Ty Cobb 1910 .383
70 Jesse Burkett 1897 .383
71 Tris Speaker 1912 .383
72 Ty Cobb 1917 .383
73 Lefty O'Doul 1930 .383
74 Joe Jackson 1920 .382
75 Ty Cobb 1918 .382
76 Honus Wagner 1900 .381
77 Babe Herman 1929 .381
78 Joe DiMaggio 1939 .381
79 Al Simmons 1930 .381
80 Paul Waner 1927 .380
81 Rogers Hornsby 1929 .380
82 Billy Hamilton 1893 .380
83 Tris Speaker 1923 .380
84 Goose Goslin 1928 .379
85 Freddy Lindstrom 1930 .379
86 Larry Walker 1999 .379
87 Willie Keeler 1899 .379
88 Lou Gehrig 1930 .379
89 John Cassidy 1877 .378
90 Pete Browning 1882 .378
91 Ty Cobb 1925 .378
92 Babe Ruth 1924 .378
93 Sam Crawford 1911 .378
94 Tris Speaker 1922 .378
95 Earl Averill 1936 .378
96 Babe Ruth 1921 .378
97 Heinie Manush 1928 .378
98 Heinie Manush 1926 .378
99 Ed Delahanty 1897 .377
100 Willie Keeler 1895 .377
101 Ty Cobb 1909 .377
102 Cy Seymour 1905 .377
103 Stan Musial 1948 .376
104 Ed Delahanty 1902 .376
105 Nap Lajoie 1904 .376
106 Jesse Burkett 1901 .376
107 Babe Ruth 1920 .376
108 Zack Wheat 1924 .375
109 Joe Medwick 1937 .374
110 Dan Brouthers 1883 .374
111 Lou Gehrig 1928 .374
112 Jake Stenzel 1895 .374
113 Lou Gehrig 1927 .373
114 Pete Browning 1890 .373
115 Dan Brouthers 1889 .373
116 Joe Jackson 1913 .373
117 Dave Orr 1890 .373
118 Babe Ruth 1931 .373
119 Paul Waner 1936 .373
120 Sam Thompson 1887 .372
121 Todd Helton 2000 .372
122 Nomar Garciaparra 2000 .372
123 Bill Terry 1929 .372
124 Ichiro Suzuki 2004 .372
125 Eddie Collins 1920 .372
126 Tommy Tucker 1889 .372
127 Bug Holliday 1894 .372
128 Babe Ruth 1926 .372
129 Heinie Zimmerman 1912 .372
130 Tony Gwynn 1997 .372
131 Roger Connor 1885 .371
132 Willie Keeler 1894 .371
133 George Sisler 1921 .371
134 Cap Anson 1886 .371
135 Jim Bottomley 1923 .371
136 Ty Cobb 1916 .371
137 Charlie Gehringer 1937 .371
138 Al Wingo 1925 .370
139 Paul Waner 1928 .370
140 Andres Galarraga 1993 .370
141 Dan Brouthers 1886 .370
T142 Tony Gwynn 1987 .370
T142 Rogers Hornsby 1920 .370
144 Sam Thompson 1893 .370
145 Barry Bonds 2002 .370
146 Benny Kauff 1914 .370
147 Ty Cobb 1915 .369
148 Ted Williams 1948 .369
149 Billy Hamilton 1898 .369
150 Lew Fonseca 1929 .369
151 John McGraw 1895 .369
152 Mike Tiernan 1896 .369
T153 Cal McVey 1877 .368
T153 Paul Waner 1930 .368
155 Nap Lajoie 1912 .368
156 Tony Gwynn 1995 .368
T157 Ed Delahanty 1893 .368
T157 Lefty O'Doul 1932 .368
159 Chuck Klein 1933 .368
160 Wade Boggs 1985 .368
161 Dan Brouthers 1882 .368
162 Jeff Bagwell 1994 .368
163 Jack Doyle 1894 .367
164 Elmer Flick 1900 .367
165 Jim Bottomley 1925 .367
166 Denny Lyons 1887 .367
167 Harry Heilmann 1926 .367
168 Steve Brodie 1894 .366
169 Wade Boggs 1988 .366
T170 Larry Walker 1997 .366
T170 Pie Traynor 1930 .366
172 Rico Carty 1970 .366
173 George Hall 1876 .366
174 Stan Musial 1946 .365
175 Billy Hamilton 1896 .365
176 Eddie Collins 1911 .365
177 Mickey Mantle 1957 .365
178 Al Simmons 1929 .365
179 Joe Kelley 1895 .365
180 Johnny Mize 1937 .364
181 Joe Kelley 1896 .364
182 Jimmie Foxx 1932 .364
183 Rod Carew 1974 .364
184 Tris Speaker 1913 .363
185 Larry Walker 1998 .363
186 Jesse Burkett 1900 .363
187 Honus Wagner 1905 .363
T188 John Olerud 1993 .363
T188 Wade Boggs 1987 .363
190 Chicken Wolf 1890 .363
191 Joe Torre 1971 .363
192 Lou Gehrig 1934 .363
193 Harry Walker 1947 .363
194 Hugh Duffy 1893 .363
195 Joe Kelley 1897 .362
196 Willie Keeler 1900 .362
197 Paul Waner 1934 .362
198 Jim O'Rourke 1877 .362
199 Cap Anson 1882 .362
200 Barry Bonds 2004 .362
201 Pete Browning 1885 .362
202 Tris Speaker 1921 .362
203 Riggs Stephenson 1929 .362
204 Elmer Smith 1896 .362
205 Mike Piazza 1997 .362
206 Nap Lajoie 1897 .361
207 Charlie Hickman 1902 .361
208 Jake Stenzel 1896 .361
209 Rogers Hornsby 1927 .361
210 Wade Boggs 1983 .361
211 Jimmy Ryan 1894 .361
212 Norm Cash 1961 .361
213 Eddie Collins 1923 .360
214 George Gore 1880 .360
215 Jim O'Rourke 1890 .360
T216 Jimmie Foxx 1939 .360
T216 Orator Shaffer 1884 .360
218 Kiki Cuyler 1929 .360
219 Babe Ruth 1930 .359
220 Rod Carew 1975 .359
221 Carl Reynolds 1930 .359
222 Zack Wheat 1925 .359
223 Dan Brouthers 1885 .359
224 Albert Pujols 2003 .359
225 Paul O'Neill 1994 .359
226 Bob Fothergill 1927 .359
227 Charlie Jamieson 1924 .359
228 Cecil Travis 1941 .359
229 Todd Helton 2003 .358
T230 George Burns 1926 .358
T230 Mike Griffin 1894 .358
232 Bill Everitt 1895 .358
233 George Stone 1906 .358
234 Paul Hines 1878 .358
235 Tony Gwynn 1993 .358
236 Alex Rodriguez 1996 .358
237 Freddy Lindstrom 1928 .358
238 Jesse Burkett 1894 .358
239 Ed McKean 1894 .357
240 Mickey Cochrane 1930 .357
241 Roberto Clemente 1967 .357
T242 Nomar Garciaparra 1999 .357
T242 Ty Cobb 1927 .357
T242 Bob Caruthers 1887 .357
245 Dixie Walker 1944 .357
246 Dave Foutz 1887 .357
T247 Roger Connor 1883 .357
T247 Paul Hines 1879 .357
249 Wade Boggs 1986 .357
250 Albert Belle 1994 .357
251 Ken Williams 1923 .357
T252 Ginger Beaumont 1902 .357
T252 Joe DiMaggio 1941 .357
254 Bill Dahlen 1894 .357
T255 Stan Musial 1943 .357
T255 Kiki Cuyler 1925 .357
257 Earle Combs 1927 .356
258 Mike Donlin 1905 .356
259 Ted Williams 1942 .356
T260 Edgar Martinez 1995 .356
T260 Kirby Puckett 1988 .356
262 Charlie Gehringer 1934 .356
263 Harry Heilmann 1922 .356
264 Jimmie Foxx 1933 .356
265 Cap Anson 1876 .356
266 Ed Swartwood 1883 .356
267 Elmer Smith 1894 .356
268 Bill Lamar 1925 .356
T269 Pie Traynor 1929 .356
T269 Babe Ruth 1927 .356
T269 Hack Wilson 1930 .356
272 Chuck Klein 1929 .356
273 Ross Youngs 1924 .356
274 Nap Lajoie 1906 .355
275 Honus Wagner 1903 .355
T276 Cupid Childs 1896 .355
T276 Phil Cavarretta 1945 .355
278 Heinie Manush 1929 .355
279 Lou Boudreau 1948 .355
280 Hughie Jennings 1897 .355
281 George Davis 1893 .355
282 Kiki Cuyler 1930 .355
283 Darin Erstad 2000 .355
284 Bobby Veach 1919 .355
285 Jimmy Williams 1899 .355
286 Bill Joyce 1894 .355
287 Baby Doll Jacobson 1920 .355
288 Stan Musial 1951 .355
289 Roger Connor 1886 .355
290 Moises Alou 2000 .355
T291 Lloyd Waner 1927 .355
T291 Hank Aaron 1959 .355
293 Oyster Burns 1894 .354
294 Fielder Jones 1896 .354
295 Jake Stenzel 1894 .354
296 Jack Doyle 1897 .354
297 Johnny Hodapp 1930 .354
T298 Ed Delahanty 1901 .354
T298 Abner Dalrymple 1878 .354
300 Charlie Gehringer 1936 .354
301 Tony Lazzeri 1929 .354
302 Bill Madlock 1975 .354
303 Kiki Cuyler 1924 .354
304 Lou Gehrig 1936 .354
305 King Kelly 1884 .354
306 Jimmie Foxx 1929 .354
307 Chick Stahl 1897 .354
T308 Honus Wagner 1908 .354
T308 Goose Goslin 1926 .354
310 Bill Terry 1934 .354
311 Paul Waner 1937 .354
312 Jimmy Sheckard 1901 .354
313 Billy Goodman 1950 .354
314 Dave Orr 1884 .354
315 John Olerud 1998 .354
316 Ray Grimes 1922 .354
317 Lloyd Waner 1929 .353
318 Frank Thomas 1994 .353
319 Honus Wagner 1901 .353
320 Joe Medwick 1935 .353
321 Ralph Garr 1974 .353
T322 Harvey Kuenn 1959 .353
T322 Willie McGee 1985 .353
324 Cupid Childs 1894 .353
325 Gee Walker 1936 .353
326 Mickey Mantle 1956 .353
327 Paul Molitor 1987 .353
328 Wilbert Robinson 1894 .353
329 Mickey Vernon 1946 .353
330 Joe Sewell 1923 .353
331 Jake Stenzel 1897 .353
332 George Davis 1897 .353
333 Tony Gwynn 1996 .353
334 George Sisler 1917 .353
335 George Burns 1918 .352
336 Ginger Beaumont 1899 .352
337 Joe DiMaggio 1940 .352
338 Bill Dahlen 1896 .352
339 Baby Doll Jacobson 1921 .352
340 George Sisler 1919 .352
341 Jack Glasscock 1889 .352
T342 Tommy Holmes 1945 .352
T342 George Davis 1894 .352
344 Hugh Duffy 1895 .352
345 Cecil Cooper 1980 .352
346 Hack Miller 1922 .352
347 Tris Speaker 1917 .352
348 Jack Tobin 1921 .352
349 Bibb Falk 1924 .352
350 Don Mattingly 1986 .352
351 Lou Gehrig 1937 .351
352 Tony Gwynn 1984 .351
353 Tom McCreery 1896 .351
354 Jack Fournier 1923 .351
355 Roberto Clemente 1961 .351
356 Bob Ferguson 1878 .351
357 Hardy Richardson 1886 .351
358 Al Simmons 1928 .351
359 Fred Clarke 1903 .351
360 John Peters 1876 .351
361 Ross Youngs 1920 .351
362 Edd Roush 1923 .351
363 Joe Start 1878 .351
364 Mike Donlin 1903 .351
365 Manny Ramirez 2000 .351
366 Joe Jackson 1919 .351
367 Chick Stahl 1899 .351
368 Eddie Morgan 1931 .351
369 Joe Medwick 1936 .351
370 Stan Musial 1957 .351
371 George Van Haltren 1896 .351
372 Jack Fournier 1925 .350
T373 Frank Demaree 1936 .350
T373 Ty Cobb 1907 .350
375 Jake Daubert 1913 .350
376 Tommy McCarthy 1890 .350
377 Heinie Manush 1930 .350
378 Austin McHenry 1921 .350
379 Carson Bigbee 1922 .350
380 Larry Walker 2001 .350
T381 Rod Carew 1973 .350
T381 Dick Porter 1930 .350
383 Bill Terry 1932 .350
384 Dan Brouthers 1891 .350
385 Sam Rice 1925 .350
386 Roger Bresnahan 1903 .350
387 Ichiro Suzuki 2001 .350
388 Jimmy Bannon 1895 .350
389 Richie Ashburn 1958 .350
390 Honus Wagner 1907 .350
Pre 1900: Hugh Duffy of the Boston Braves hit .440 in 1894. After 1900: Napolean LaJoie of the Philadelphia Phillies hit .426 in 1901.
.390 in 1980
Hugh Duffy of the 1894 Boston Beaneaters.
Clemente hit .357 for the Pittsburgh Pirates in 1967, his highest batting average in any one season during his career. Incidently, the Pirates finished 6th in the 10 team National League that season with an 81-81 record.
Chipper Jones won the 2008 National League Batting title with a .364 batting average, and Joe Mauerwon the 2008 American League batting title with a .328 batting Average.
Dustin Pedroia
Roger Hornsby highest batting average in a season was .424 in 1924.
Derek Jeter's highest batting average was .349, it was the 1999 season.
.390 in 1980
As of the 7th game in the 2011-2012 season the phillies are in 1st in batting average batting .337
As far as the major leagues go, Derek Jeter's highest batting average was .349, it was the 1999 season.
John Olerud holds the record for highest batting average by a New York Met in a single season with .354 in 1998
Hugh Duffy of the 1894 Boston Beaneaters.
because the world series
Clemente hit .357 for the Pittsburgh Pirates in 1967, his highest batting average in any one season during his career. Incidently, the Pirates finished 6th in the 10 team National League that season with an 81-81 record.
josh Hamilton who finished out the season hitting 359
Chipper Jones won the 2008 National League Batting title with a .364 batting average, and Joe Mauerwon the 2008 American League batting title with a .328 batting Average.
That would be Darren Erstad, who batted .355 in the 2000 season.