Who has the most RBI in one inning?

Third baseman Fernando Tatis holds the record with eight RBI in an inning. In the third inning of an April 23, 1999 game against the Los Angeles Dodgers, Tatis stepped to the plate with the bases loaded, and deposited a Chan Ho Park pitch over the outfield wall. The rest of the Cards’ lineup also got on base against Park, again bringing up Tatis with the bases loaded. And again, Tatis sent Park’s offering high into the night. Another grand slam, another four ribbies. Since 1900, no other player has knocked in more than six runs in an inning. Beating Tatis’s record will be difficult, since a player must come to bat three times in one inning just to have the opportunity.