What Is a Grand Slam in Baseball?

A grand slam is a home run hit with the bases loaded — runners on first, second, and third base — so it scores all three runners plus the batter for four total runs, the maximum any single play can produce in baseball.

How a grand slam happens

There’s no special rule that creates a grand slam; it’s simply the label given to any home run hit while every base is occupied. For a grand slam to happen, three things have to line up: a runner on first, a runner on second, a runner on third, and then the batter drives the ball out of play (over the fence, or in rare cases around the bases before the defense can retire him on an inside-the-park homer). Since the bases can only ever hold three runners at once, four runs is the ceiling for any single plate appearance — which is exactly what makes the grand slam the most valuable hit in the sport.

Why it scores four runs

Baseball only allows three baserunners on base at any time (first, second, third), plus the batter at the plate. When the batter’s ball clears the fence with all three bases loaded, every runner is forced to score, followed by the batter himself as he completes his own trip around the bases. That’s four runs from one swing, turning a single at-bat into what would otherwise take multiple hits, walks, or productive outs to manufacture.

Where the name comes from

“Grand slam” isn’t originally a baseball term — it comes from the card game bridge, where a “grand slam” means winning every possible trick in a hand. Baseball borrowed the phrase because a bases-loaded home run does the batting equivalent: it clears out every runner on base and maximizes the damage of a single play, the same way a grand slam in bridge maximizes the value of a hand. Broadcasters sometimes use colorful nicknames for the play too, most famously longtime Seattle Mariners announcer Dave Niehaus, who called it a “grand salami.”

Walk-off and ultimate grand slams

A walk-off grand slam ends the game on the spot because it comes in the home team’s last at-bat and puts them ahead, so the game is over the instant the go-ahead run crosses the plate — teammates often swarm the batter at home plate before he can finish circling the bases. The rarest version is the ultimate grand slam: a walk-off slam hit when the batting team was trailing by exactly three runs with two outs in their final at-bat, turning what should have been a loss into a precise one-run win in a single swing. It’s considered one of the most dramatic plays in the sport because it combines the biggest possible hit with the highest possible stakes.

Grand slam records

Category	Record holder(s)	Total
Career grand slams	Alex Rodriguez	25
Career grand slams (2nd)	Lou Gehrig	23
Career grand slams (3rd)	Manny Ramirez	21
Single-season grand slams	Don Mattingly (1987), Travis Hafner (2006)	6
First MLB grand slam	Roger Connor, September 10, 1881	—
Two grand slams, same inning	Fernando Tatis, 1999	—
Two grand slams in a game, by a pitcher	Tony Cloninger, 1966	—

Alex Rodriguez’s 25 career grand slams put him well clear of Lou Gehrig and Manny Ramirez, and his record reflects both his power and his longevity in the middle of a lineup. On the single-season side, Don Mattingly’s six grand slams in 1987 are especially notable because he never hit another one in his entire career — every grand slam he ever hit came in that single, historic season.

Grand slams in the postseason and World Series

Grand slams carry extra weight when they happen on the biggest stage. The first grand slam in World Series history came off the bat of Elmer Smith for the Cleveland Indians in 1920, and the moment has been echoed many times since. In the 2024 World Series, Freddie Freeman hit the first walk-off grand slam in World Series history in Game 1, an instant classic that swung momentum for the Los Angeles Dodgers. A year later, Addison Barger delivered the first pinch-hit grand slam in World Series history, showing that even a player coming off the bench can produce the biggest hit of a game. Teams have also stacked multiple slams in a single postseason game — the Boston Red Sox became the first club to hit two grand slams in one postseason contest during Game 2 of the 2021 ALCS. These moments tend to be remembered for years, since a grand slam in a close playoff game can single-handedly decide a series.

Grand slam vs. other big hits

A grand slam is often compared to other high-run plays, but it stands alone because it requires the bases to be completely loaded. A three-run homer with runners on second and third, for example, drives in the same number of runners minus one — it’s a big hit, but it isn’t a grand slam unless first base was occupied too. Understanding this distinction matters when reading a box score or following live play-by-play, since only bases-loaded home runs get the grand slam label.

Where it fits in baseball strategy

A grand slam is the payoff for situations that pitchers work hard to avoid: getting into trouble with runners on and then loading the bases rather than pitching around a hitter. It’s closely tied to other bases-loaded and scoring plays covered in our baseball terminology glossary, including the sacrifice fly, which also drives in runs from a fly ball but without clearing the bases, and the bunt, a small-ball tactic teams sometimes use instead of swinging away in bases-loaded situations. For more explainers like this one, see our full library of baseball and MLB guides.