Guinness World Records said the 34-year-old duke of Sussex and 37-year-old duchess of Sussex reached 1 million followers in five hours and 45 minutes Tuesday after launching @sussexroyal.
K-pop star Kang Daniel set the previous record in January, reaching 1 million followers in 11 hours and 36 minutes. Harry and Markle had over 2.6 million followers as of Wednesday morning.
Harry and Markle shared a slideshow of photos Tuesday as their first post. The pictures show the couple on various outings around the world.
"Welcome to our official Instagram; we look forward to sharing the work that drives us, the causes we support, important announcements, and the opportunity to shine a light on key issues. We thank you for your support, and welcome you to @sussexroyal," the couple said in the caption.
Markle, an actress known for the USA Network series Suits, had deleted her blog and social media accounts following her engagement to Prince Harry in November 2017. The couple married in May and announced in October they are expecting their first child.
News broke in March Harry and his brother, Prince William, are splitting their royal household. Harry and Markle will move from Kensington Palace to Frogmore Cottage and establish an office in Buckingham Palace.
"This long-planned move will ensure that permanent support arrangements for The Duke and Duchess's work are in place as they start their family and move to their official residence at Frogmore Cottage," the palace said.