The Brit won the FIA European F3 Championship last season which followed after title triumphs in Formula Renault 2.0, New Zealand's Toyota Racing Series in 2016 and Britain's Formula 4 Championship.
This year Norris is in contention for the Formula 2 title in his debut season in the category.
McLaren has recently been evaluating Norris for a race seat having handed the teenager outings in free practice at Spa and Monza.
“To be announced as a race driver for McLaren is a dream come true,” said Norris.
“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.
“For the remainder of 2018, my focus remains firmly on the Formula 2 championship.
“My objective is to win the title before joining McLaren full-time, which will be tough, but I will fight as hard as I can for the remaining four races.
“I'll also be working closely with McLaren at every opportunity to learn as much as possible from the drivers, engineers and mechanics to give myself the best preparation ahead of next year.”
McLaren CEO Zak Brown believes Norris will play an integral part in rebuilding the former world championship winning team's fortunes.
“We're very pleased to finally be able to reveal who will complete our driver line-up at McLaren for 2019,” said Brown.
“We believe Lando is an exciting talent, full of potential, who we've very deliberately kept within the McLaren fold for exactly that reason.
“We already know he's fast, he learns quickly, and has a mature head on his young shoulders. We see much potential for our future together.
“The investment we have made in his budding career with simulator development and seat-time in the car has been well-deserved, as he has continued to prove his abilities both behind the wheel and in his work with the engineering team.
“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.”