Disnye's photorealistic computer-animated remake of the beloved 1994 classic boasts a star-studded cast, including Donald Glover as king-in-waiting Simba and Beyonce Knowles-Carter voicing his love interest Nala.
Former actress Meghan, who is on maternity leave following the birth of son Archie, waved at waiting crowds as she arrived with her husband in London’s Leicester Square.
The Duchess wore a black dress, with full length sleeves and heels with her hair swept up in a bun.
The royal couple were joined by a dazzling array of stars and met some of the cast and crew before watching the film, including Beyonce and her husband Jay-Z.
Meghan warmly embraced the singer, with Beyonce saying: "We love you guys" and rapper, Jay-Z, could be heard saying "congrats" while his wife said "baby, so beautiful."
It is believed to be the first time the two couples have met.
Harry kissed Beyonce on both cheeks and appeared to mention that the American couple were a busy pair.
The singer appeared to answer: "A little bit. No more busy than you guys."
Meanwhile, Harry complimented Pharrell Williams on his outfit, describing his black shorts, white socks and black shoes combination as "strong".
The premiere is being held in “support of the conservation and communities work of His Royal Highness through The Royal Foundation”, Buckingham Palace said.
Afterward the film, the royal couple greeted representatives from organisations doing groundbreaking work in the areas of conservation and the environment.
Disney has announced its global conservation campaign Protect the Pride to mark the movie’s release.
With conservation partners and the Royal Foundation, the drive aims to raise awareness and support efforts to recover the dwindling lion population across Africa.
Buckingham Palace said: “The Duke of Sussex has taken a deep personal interest in frontline conservation projects that work to protect Africa’s natural heritage and support both wildlife and local communities.”
The couple are taking baby Archie to South Africa in the autumn and the Duke is also carrying out solo visits to Angola, Malawi and Botswana.
Meghan was out and about with Archie and Harry on Wednesday at a charity polo match with Prince William and Kate and their children, Prince George, Prince Louis and Princess Charlotte.
She also made two trips to Wimbledon to watch her close friend Serena Williams play, including at the women's final on Saturday.
The Sussexes’ approach to privacy has made headlines after they decided not to reveal details of Archie’s godparents following his private christening, and after a royal protection officer asked a Wimbledon fan, who was photographing Serena Williams, not to take pictures of Meghan.