The Royals will now play their first World Series since 1985, when they last made the playoffs.
"It's been an amazing run. This is great," said left fielder Alex Gordon, who made another jarring catch. "We've been playing pretty good baseball. It's nothing better than when you win. Today, same old story: good pitching, good defense and scratch out a win."
Outfielder Lorenzo Cain was selected Most Valuable Player of the ALCS, batting .533 and leading an outstanding defense.
After holding the Orioles to three hits in Game 3 on Tuesday night, Jason Vargas and the Royals bullpen nearly turned the trick again. Kelvin Herrera and Wade Davis ushered the game to Holland, who matched Dennis Eckersley's record by saving his fourth game in the ALCS.
After Holland got J.J. Hardy to ground out to third base for the final out, the Royals spilled onto the infield in a wild celebration. Fireworks shot over the crown-shaped scoreboard in center field, and a blue-clad sellout crowd that included Royals great George Brett let out a roar.
Kansas City will host the first two World Series games beginning Tuesday. Coincidentally, it was the Cardinals who the Royals beat for their only World Series title in a dramatic seven-game series.
Regardless of the opponent, the Royals will carry an 11-game playoff win streak into the World Series, one shy of the major league record. That includes winning their first eight games this season, something that had never been done in postseason history. Kansas City beat Oakland in the wild card and swept the Los Angeles Angels in the Division Series.
"We know once we have the lead, we've got the best pitching staff and the best bullpen around. So we've got to get them the lead," said Eric Hosmer, who drove in a run. "We're not done. We ain't done yet."
The Orioles, meanwhile, will limp into the offseason after their first sweep in 21 playoff series, dating to the days when the club was called the St. Louis Browns.