The 1991 SummerSlam was the fourth annual SummerSlam professional wrestling pay-per-view (PPV) event produced by the World Wrestling Federation (WWF, now WWE). It took place on Monday, August 26, 1991, at Madison Square Garden in New York City, New York. Nine matches were contested at the event, including a dark match held before the live broadcast. This was the second event to take place in Madison Square Garden, the first since 1988.

SummerSlam 1991 is remembered for the on-screen wedding of Randy Savage and Miss Elizabeth, dubbed "A Match Made in Heaven" by announcer Gene Okerlund. Savage and Elizabeth had been married in real life since December 1984. WWF personalities shown at the reception afterward included Bobby Heenan, Gene Okerlund, J. J. Dillon, The Undertaker, and Jake Roberts. The last two were uninvited guests. Roberts proceeded to frighten Elizabeth with his snake while Undertaker attacked Savage with an urn.

This was contrasted with "A Match Made in Hell", the main event of the show, which was a handicap tag team match between WWF Champion Hulk Hogan and The Ultimate Warrior against Sgt. Slaughter, General Adnan, and Colonel Mustafa. It was Slaughter's final on-screen appearance as an Iraqi sympathizer, a storyline fueled by the Gulf War.

Among the other on-screen highlights of the event was The Legion of Doom (Animal and Hawk) defeating The Nasty Boys (Brian Knobbs and Jerry Sags) to win the WWF Tag Team Championship. The team became the only tag team in wrestling history to have held the WWF Tag Team Championship, the NWA World Tag Team Championship, and the AWA World Tag Team Championship. Another highlight was Bret Hart winning his first singles championship in the WWF when he defeated Mr. Perfect for the WWF Intercontinental Heavyweight Championship. After winning the match, Hart climbed into the stands to hug his parents Stu and Helen Hart.