"This is the greatest moment of my personal baseball career," Ellis said. "It's really humbling, just to be a part of where this team is headed right now. It feels real special."
Wesley Wright (0-1) opened the ninth by hitting Andre Ethier with an 0-2 pitch. Scott Van Slyke batted for reliever Kenley Jansen (4-0) and advanced Ethier with a sacrifice bunt. Wilton Lopez intentionally walked James Loney, and Ellis drove a 1-1 pitch into the left-field pavilion for his fifth homer.
"I faced that guy a few times in Houston, and he likes to work the sinker," Ellis said. "He's a tough pitcher, so you've just got to find a pitch up in the zone. I was just kind of looking for something elevated, and I was able to find a fastball to hit. I tried to put a good aggressive swing on it and drive it to the outfield."
Billingsley threw 73 of his 99 pitches during the first three innings and retired only eight of his first 16 batters, but all the Astros could scrape across was two runs.
The missed opportunities eventually came back to haunt the Astros, who squandered a chance to get back to the .500 mark for the first time since April 14, when they were 4-4.
"I was locating pretty well and had pretty good off-speed stuff, which helped me escape with just a minimum amount of damage and keep the team in the game," Billingsley said. "It was a great team win. What's great about this team is that it's somebody different every day and everybody's stepping up when their time comes. A.J.'s been stepping up a lot this year in big situations."
The Dodgers' 11th victory in 15 games improved the best record in the majors to 31-15 and extended their NL West lead over San Francisco to a season-high 7 1-2 games -- the largest margin in any division.
Jansen pitched 1 1/3 innings for the victory. The right-hander came in with two-out in the eighth, trying to protect a 3-2 lead for Billingsley after Ronald Belisario issued a pair of two-out walks.
Brian Bogusevic scored the tying run when Jason Castro slapped a ground single off the glove of third baseman Jerry Hairston Jr. and into foul territory, but Jansen retired Jordan Schafer on a flyball with the bases loaded.
Billingsley allowed two runs and five hits in five innings, striking out eight and walking three. He is 0-3 with a 5.01 ERA in eight starts since beating San Diego and Pittsburgh in his first two outings this season.
"He grinded and battled," Ellis said. "His pitch count really ran up high, but the way he settled down in the fourth and fifth innings helped restore order -- especially when we got the lead back. One thing you can say about Chad is that he always competes. He gives you everything he has out there and never lets anything really bother him on the mound. And he has the ability to pitch himself out of tough jams, which he did again tonight."
Billingsley had three strikeouts in the first, but in between them were Jose Altuve's double and Carlos Lee's run-scoring single. A bases-loaded walk to Schafer forced in another run in the second. But Billingsley came back to strike out Altuve, and Ethier -- who won his first Gold Glove last season -- helped minimize the damage with an inning-ending diving catch of J.D. Martinez's sinking line drive to right field. Houston stranded two more in the third when Castro took a called third strike.
"I felt like we had him for sure, especially in that inning when we had the bases loaded," Martinez said. "The ball that I hit to Ethier that he made a nice play on -- if that falls or gets by him, it's probably a different outcome to the game. Billingsley got away with one there. He was able to work through it and get out of jams."
Houston's Bud Norris threw 116 pitches over 4 2/3 innings, allowing three runs, eight hits and four walks. The right-hander's early departure snapped a string of 38 consecutive games by the Astros in which their starters lasted at least five innings. Norris ended May 4-0 in five starts with a 1.17 ERA.
Ethier got the Dodgers on the board in the third with a two-out run-scoring double that raised his NL-leading RBIs total to 41.
One inning later, left fielder Martinez robbed Ellis of a potential RBI double with a running catch in the alley before slamming into the fence. Dee Gordon followed with a double that sent Loney to third, and Tony Gwynn Jr. put Los Angeles ahead 3-2 with a two-run, two-out single through the right side.
Ethier had a chance to break open the game later that inning, but lined out to center with the bases loaded.
Los Angeles Kings centers Mike Richards and Jeff Carter attended the game in front-row seats adjacent to the owners' box while awaiting Game 1 of the Stanley Cup finals next Wednesday at New Jersey. ... The previous time an Astros starter didn't go at least five innings was April 13, when Lucas Harrell was removed after four in a no-decision at Miami. ... Loney had three hits -- two of them against Norris, making Loney 7 for 14 career against him.