How many players hit over 40 home runs in a major league baseball season?

As of the 2008 season, 121 different MLB players had hit 40+ home runs in a season a total of 293 times:

Adam Dunn

Adrian Beltre

Al Rosen

Albert Belle

Albert Pujols

Alex Rodriguez

Alfonso Soriano

Andre Dawson

Andres Galarraga

Andruw Jones

Babe Ruth

Barry Bonds

Ben Oglivie

Billy Williams

Brady Anderson

Carl Yastrzemski

Carlos Beltran

Carlos Delgado

Carlos Pena

Cecil Fielder

Chipper Jones

Chuck Klein

Cy Williams

Dale Murphy

Dante Bichette

Darrell Evans

Dave Kingman

Davey Johnson

David Justice

David Ortiz

Derrek Lee

Dick Allen

Dick Stuart

Duke Snider

Eddie Mathews

Ellis Burks

Ernie Banks

Frank Howard

Frank Robinson

Frank Thomas

Gary Sheffield

George Bell

George Foster

Gil Hodges

Gorman Thomas

Greg Vaughn

Gus Zernial

Hack Wilson

Hal Trosky

Hank Aaron

Hank Greenberg

Hank Sauer

Harmon Killebrew

Jason Giambi

Javy Lopez

Jay Buhner

Jeff Bagwell

Jeff Burroughs

Jermaine Dye

Jesse Barfield

Jim Edmonds

Jim Gentile

Jim Rice

Jim Thome

Jimmie Foxx

Joe DiMaggio

Johnny Bench

Johnny Mize

Jose Canseco

Juan Gonzalez

Ken Caminiti

Ken Griffey

Kevin Mitchell

Lance Berkman

Larry Walker

Lou Gehrig

Luis Gonzalez

Manny Ramirez

Mark McGwire

Mark Teixeira

Matt Williams

Mel Ott

Mickey Mantle

Mike Piazza

Mike Schmidt

Mo Vaughn

Norm Cash

Orlando Cepeda

Paul Konerko

Phil Nevin

Prince Fielder

Rafael Palmeiro

Ralph Kiner

Reggie Jackson

Richard Hidalgo

Richie Sexson

Rico Petrocelli

Rocky Colavito

Roger Maris

Rogers Hornsby

Roy Campanella

Roy Sievers

Ryan Howard

Ryne Sandberg

Sammy Sosa

Shawn Green

Ted Kluszewski

Ted Williams

Tino Martinez

Todd Helton

Todd Hundley

Tony Armas

Tony Batista

Tony Perez

Travis Hafner

Troy Glaus

Vinny Castilla

Vladimir Guerrero

Wally Post

Willie McCovey

Willie Stargell

Willie Mays