St. Valentine's Day Massacre: In Your House was the 27th In Your House professional wrestling pay-per-view (PPV) event produced by the World Wrestling Federation (WWF; later WWE in 2002). It took place on February 14, 1999, at the Memphis Pyramid in Memphis, Tennessee. The title of the event alludes to the Saint Valentine's Day massacre in the year 1929, which saw seven people murdered as a part of the gang war between Al Capone and Bugs Moran. The event saw the WWF debut of Paul Wight, formerly known as The Giant in World Championship Wrestling (WCW), and who would later be renamed to The Big Show. It was the final In Your House event until June 2020, as at the time, the WWF moved to install permanent names for their monthly PPVs, which began with Backlash in April 1999.

Eight professional wrestling matches were scheduled on the event's card. The first main event was that of the WWF Championship. As The Rock and Mankind had fought many times previously with ambiguous match endings, it was decided the match would be a Last Man Standing match, a match where a wrestler loses if they cannot stand up before the referee counts to ten. The second main event was a steel cage match between "Stone Cold" Steve Austin and the owner of the company, Vince McMahon, to decide whether Austin would go on to headline WrestleMania XV the following month.