The 6-foot-5 De La Cruz, who primarily plays shortstop, was promoted from Triple-A Louisville and will join the Reds on Tuesday for the team's series against the Los Angeles Dodgers. He takes the roster spot of third baseman Nick Senzel, who was placed on the injured list with a right knee injury.
De La Cruz, with a tantalizing power-speed combination, was named baseball's top prospect by ESPN's Kiley McDaniel in his updated rankings last month.
"I knew this day was going to come," De La Cruz said through a translator. "But it didn't mean that I was going to be weird about it or anything like that. I was just enjoying my moment out there (in the minors), playing out there like it was my last day and just enjoying the moment while I was there.
"Honestly, I'm just really excited to be here right now. I'm ready to help out this team. I'm excited to get everything going right now."
The 21-year-old is hitting .296 with 12 home runs, 11 stolen bases, 36 RBIs and an OPS of 1.031 in 158 at-bats this season. He started the season on the injured list after suffering a left hamstring strain during spring training.
Signed out of the Dominican Republic as a teenager, De La Cruz hit 28 homers and stole 47 bases across Class A and Double-A last year.
"We've talked about this a lot," Reds manager David Bell said. "We knew Elly was going to be here. We got to know him in spring training. There's a lot of players that are young players in our system that are going to be here over time. You don't know for sure when that's going to be.
"A lot of times, they just have to dictate when they're ready, and that's what Elly did. He went and played extremely well not only on the field, but just the way he approaches the game and the way he works. All the things that we're looking for to add a player into our team and help us win."
Senzel, who was a late scratch on Monday, is hitting .258 with four home runs and 27 RBIs this season.
The Reds have remained around the periphery of the NL wild-card race this season thanks to big contributions from young players. Rookie Matt McLain has hit .329 while filling in at shortstop, 23-year-old Hunter Greene has dominated at times and Andrew Abbott pitched six scoreless innings in his major league debut Monday against Milwaukee.
"There's a reason why they were called up, because they know that they can put themselves out there and make this team better and help the team win," De La Cruz said. "That's why I'm up here too."
The Associated Press contributed to this report.