The 2018 Astros Opening Day game may just be the biggest opening day game in Astros’ history. The defending World Series Champions will play the Baltimore Orioles for opening day, but the matchup itself is not the best part of opening day. The Houston Astros will also receive their World Series rings and raise the championship flag before the game begins. The Houston Astros Opening Day game takes place on April 2, 2018 at Minute Maid Park. While the game starts at 7:10pm, you will want to get there early to witness history, as the Astros will hold their first ever World Series championship ring and flag ceremony.