In baseball, a home run is credited to a batter when he hits a fair ball and reaches home safely on the same play, without the benefit of an error.^[1] 135 players have hit a home run in their first at bat of a Major League Baseball (MLB) game to date,^{[upper-alpha 1]} the most recent being Jasson Dominguez of the New York Yankees on September 1, 2023.^[3] George Tebeau and Mike Griffin both hit home runs in their first at bats on April 16, 1887. Both players are recognized as the first player to homer in his first major league at bat because the exact time when each home run was hit is unclear.^[4][5]

Luke Stuart, Walter Mueller, and Johnnie LeMaster hit inside-the-park home runs in their first at bats.^[6] Bill Duggleby, Jeremy Hermida, Brandon Crawford, Kevin Kouzmanoff and Daniel Nava hit grand slams in their first at bats—Kouzmanoff and Nava doing so on the first pitch.^[7] Ernie Koy and Heinie Mueller were the first players to accomplish the feat in the same game, doing so for the Brooklyn Dodgers and Philadelphia Phillies, respectively, in the first inning of Opening Day in 1938.^[8][9] This was equalled in 2016 by Tyler Austin and Aaron Judge, who became the only players to achieve the feat as teammates (playing for the New York Yankees) and in back-to-back at bats.^[8][10] Two players, Bob Nieman and Keith McDonald, each homered in their second at bat as well.^[11][12] Paul Gillespie and John Miller are the only players to hit home runs in both their first and last major league at bats;^[13][14] for Miller these were the only two home runs of his MLB career.^[15][16] For 23 players, their first at bat home run was the only home run of their major league careers. On the other hand, Gary Gaetti hit more home runs (360) than any other player to hit one in their first at bat.^[17][18]

Of the 31 players eligible for the Baseball Hall of Fame who have hit a home run in their first major league at bat, two – Earl Averill and Hoyt Wilhelm – have been elected,^[16] neither of them on the first ballot.^[19] Players are eligible for the Hall of Fame if they have played in at least 10 MLB seasons, and have either been retired for five seasons or deceased for at least six months.^[20] These requirements leave 19 players ineligible who are active and 75 players ineligible who did not play in 10 seasons.^{[upper-alpha 2]}

• List of Major League Baseball players with a home run in their final major league at bat