All Time Records	Single Season Records	MLB Milesontes
Career BA Leaders	Highest BA in a Season	No Hitters and Perfect Games
Career Hits Leaders	Most Hits in a Season	300 Wins Club
Career HR Leaders	Most HRs in a Season	3000 Strikeouts Club
Career RBI Leaders	Most RBIs in a Season	500 Home Run Club
Career Runs Leaders	Most Runs in a Season	3000 Hits Club
Career SB Leaders	Most SBs in a Season	Triple Crown Winners
Career Wins Leaders	Most Saves in a Season
Career Saves Leaders	Most K's in a Season
Career K Leaders	Lowest ERA in a Season
Career ERA Leaders

For the sake of not creating a debate, no Asterick's were included. Who is the greatest home run hitter will always be debated, but like it not, Barry Bond's 73 Home Runs in 2001 tops the list of the most home runs in a MLB season. Many thought that when Mark McGwire hit 70 in 1998, it may not get broken (see Todd McFarlen and his over $2 million baseball). 42 times a MLBer has hit over 50 home runs in a single season. The debate of steroids and MLB home run records will go on for years.

Most Home Runs in a Single MLB Season
Rank	Player	Team	HRs	Year
1	Barry Bonds	San Francisco Giants	73	2001
2	Mark McGwire	St. Louis Cardinals	70	1998
3	Sammy Sosa	Chicago Cubs	66	1998
4	Mark McGwire	St. Louis Cardinals	65	1999
5	Sammy Sosa	Chicago Cubs	64	2001
6	Sammy Sosa	Chicago Cubs	63	1999
7	Roger Maris	New York Yankees	61	1961
8	Babe Ruth	New York Yankees	60	1927
9	Babe Ruth	New York Yankees	59	1921
T10	Jimmie Foxx	Philadelphia Athletics	58	1932
	Hank Greenberg	Detroit Tigers	58	1938
	Ryan Howard	Philadelphia Phillies	58	2006
	Mark McGwire	Oakland Athletics St. Louis Cardinals	58	1997
T14	Luis Gonzalez	Arizona Diamondbacks	57	2001
	Alex Rodriguez	Texas Rangers	57	2002
T16	Ken Griffey	Seattle Mariners	56	1997
	Ken Griffey	Seattle Mariners	56	1998
	Hack Wilson	Chicago Cubs	56	1930
T19	Jose Bautista	Toronto Blue Jays	54	2010
	Ralph Kiner	Pittsburgh Pirates	54	1949
	Mickey Mantle	New York Yankees	54	1961
	David Ortiz	Boston Red Sox	54	2006
	Alex Rodriguez	New York Yankees	54	2007
	Babe Ruth	New York Yankees	54	1920
	Babe Ruth	New York Yankees	54	1928
T26	George Foster	Cincinnati Reds	52	1977
	Mickey Mantle	New York Yankees	52	1956
	Willie Mays	San Francisco Giants	52	1965
	Mark McGwire	Oakland Athletics	52	1996
	Alex Rodriguez	Texas Rangers	52	2001
	Jim Thome	Cleveland Indians	52	2002
T32	Cecil Fielder	Detroit Tigers	51	1990
	Andruw Jones	Atlanta Braves	51	2005
	Ralph Kiner	Pittsburgh Pirates	51	1947
	Willie Mays	New York Giants	51	1955
	Johnny Mize	New York Giants	51	1947
T37	Brady Anderson	Baltimore Orioles	50	1996
	Albert Belle	Baltimore Orioles	50	1995
	Prince Fielder	Milwaukee Brewers	50	2007
	Jimmie Foxx	Boston Red Sox	50	1938
	Sammy Sosa	Chicago Cubs	50	2000
	Greg Vaughn	San Diego Padres	50	1998

Updated: Mar. 25th 2011

Sources:
baseball-reference.com
baseball-almanac.com
wikipedia.org
thebaseballcube.com