Kit was all smiles this afternoon, waving to fans as he arrived at Rayne Church, near Inverurie.
Speaking outside the castle, where the pair will exchange vows, Leslie's father, Sebastian Leslie, said: "We are absolutely thrilled for Kit and Rose to be marrying today".
The couple - who played on-screen lovers Jon Snow and Ygritte - met on the fantasy show in 2012.
For the ceremony, the bride wore a long-sleeved ivory dress that was accessorised with a floral headpiece and a long veil.
The ceremony will be held at the remote Wardhill Castle in Aberdeenshire, which has been in Leslie's family for 900 years, said the Daily Mail.
On Friday, florists, caterers, and family members descended on the castle location to prepare for the big day and GOT cast members started to land at Aberdeen Airport.
The couple, both 31, who starred together in the TV blockbuster for four seasons, confirmed their engagement back in September past year. Both Kit and Rose are 31 years old.
Harington and Leslie have kept their wedding details private, but multiple media outlets have been able to confirm that it will take place this weekend at the Scottish castle because of a marriage notice they posted at the register office in the nearby town of Huntly. She began appearing on "Game of Thrones" in Season 2 until her character, the wilding Ygritte, the love interest of Harington's Jon Snow, was killed off in Season 4.
"I was going to string up some lights in some trees and do all the romantic stuff", Harington told The Jonathan Ross Show. "I popped my question a bit early", he said on Britain's "The Jonathan Ross Show".