Lando Norris will make his Formula 1 debut for McLaren in the 2019 season.
The Formula 2 championship contender has impressed the team with his recent runs in grand prix free practice sessions and has won the battle to become Carlos Sainz Jr's team-mate.
The announcement of Norris's promotion came shortly after McLaren revealed that it was not retaining Stoffel Vandoorne for 2019.
"To be announced as a race driver for McLaren is a dream come true," said the 18-year-old Briton.
"Although I've been part of the team for a while now, this is a special moment, one I could only hope would become reality.
"I'd like to thank the whole team for this amazing opportunity and for believing in me.
"I'm also extremely grateful for the commitment McLaren has already shown in my development, allowing me to build my experience in a Formula 1 car in both testing and on Fridays during the past two race weekends."
Norris has been part of the McLaren young driver programme since 2017, having won the McLaren Autosport BRDC Award the previous year.
His junior career also includes titles in European Formula 3, the Formula Renault Eurocup and NEC series, the Toyota Racing Series and what is now British Formula 4, and he is currently battling with Mercedes protege George Russell for the F2 title.
Toro Rosso had approached McLaren about Norris earlier this season, but McLaren CEO Zak Brown said the decision to give Norris the 2019 race seat showed how highly the team rated him and why it was unwilling to let him go.
"We believe Lando is an exciting talent, full of potential, who we've very deliberately kept within the McLaren fold for exactly that reason," said Brown.
"Lando is an integral part of our plan for rebuilding our Formula 1 operation for the future, and he has already developed a strong relationship with the team.
"In Lando and Carlos we have an impressive duo who, despite their relative youth, hold valuable experience in Formula 1 and with McLaren, and represent the next generation of McLaren drivers to lead the team forward.
"While our short-term focus is fixed on securing the best possible result for the remainder of the 2018 season, we're also massively motivated by the opportunities that lie ahead."
Sainz and Norris represent an all-new line-up for McLaren after Fernando Alonso's decision not to race in F1 next season and Vandoorne's departure.