SEATTLE — Jeremy Peña homered in the 18th inning, and the Houston Astros beat the Seattle Mariners 1-0 on Saturday to advance to the AL Championship Series for the sixth straight year.

Peña drove a slider from Penn Murfee deep to left-center for the rookie shortstop’s first playoff homer, proving the only run in an afternoon full of dominant pitching and empty trips to the plate. The 18 innings matched the longest game in playoff history.

Spoiling the Mariners’ first home playoff appearance since 2001, the Astros completed a three-game sweep of the ALDS. Next up is the New York Yankees or Cleveland Guardians in Game 1 of the ALCS on Wednesday.

While Yordan Alvarez got the big hits in the first two games in Houston, Pena set the table for Alvarez’s opportunities. As Game 3 made its way into its sixth hour, Peña delivered another painful blow to the Mariners that ended their short return to the postseason.

After 21 years, Mariners fans welcomed playoff baseball back to T-Mobile Park. They got their money’s worth — and then some.

Three previous playoff games reached the 18th inning before conclusion, one involving the Astros. The Astros beat the Atlanta Braves 7-6 in 18 innings in Game 4 of the 2005 NLDS on Chris Burke’s game-ending homer.

Game 2 of the 2014 NLDS between the San Francisco Giants and Washington Nationals and Game 3 of the 2018 World Series between the Los Angeles Dodgers and Boston Red Sox also went 18 innings.

But those games had runs. This one failed to produce anything until Peña’s swing on a 3-2 pitch.

The Mariners’ best scoring chance was Julio Rodríguez’s line drive that thudded off the wall in the eighth inning. They had runners in scoring position in the 13th and 17th but couldn’t get a key two-out hit against the Astros’ superb bullpen.

Luis Garcia worked five innings for the win. The Astros bullpen allowed five hits and struck out 15 following six innings from starter Lance McCullers Jr.

The Mariners bullpen was nearly just as good. After rookie George Kirby threw seven innings, nine relievers combined for 11 innings of five-hit ball.

The teams combined to strike out 42 times, topping the postseason record of 39 set by the Guardians and Tampa Bay Rays last week in their AL wild-card matchup that was scoreless for 15 innings before Oscar Gonzalez’s home run sent the Guardians to the ALDS.