Harington and Leslie's enduring romance began in 2012. The two, both 32, first met on set when their characters -- Jon Snow and Ygritte, respectively -- were on-screen lovers. Interestingly enough, they both shot their very first love scene with one another -- a memorable sex scene in a cave -- and Leslie's Ygritte was also the one to declare the endlessly memed line, "You know nothing, Jon Snow."
Harington spoke about the start of their romance in a 2016 interview with Vogue, and revealed that he fell in love with Leslie when they were filming in Iceland.
"The three weeks in Iceland when we were shooting the second season," he said when asked about his best memory of the show. "Because the country is beautiful, because the Northern Lights are magical, and because it was there that I fell in love. If you’re already attracted to someone, and then they play your love interest in the show, it becomes very easy to fall in love…”
"I fell in love in Iceland," Harington also said during his 2016 appearance on The Jonathan Ross Show. "I fell in love with my co-star."
Leslie's character was eventually shockingly killed by a young boy during a gruesome battle scene between the wildlings and crows at Castle Black in season four, though her romance with Harington lived on off-screen. Read on for more of the couple's biggest moments:
August 2012: Rumors begin that Harington and Leslie are dating
Harington and Leslie's romance was out of the bag in August 2012, when TMZ ran photos of the two holding hands during a dinner date in London. Eyewitnesses also told the outlet that the two were kissing during their meal.
January 2016: Harington and Leslie have their co-stars' approval
But it was worth the wait -- Harington and Leslie made no secret of their love for one another at The Olivier Awards at The Royal Opera House on April 3, 2016, looking adorable together while gazing into one another's eyes and beaming at the cameras.
May 2017: Harington says he and Leslie are 'very, very happy" and living together
In an Esquire interview, Harington revealed that the two made the decision to move in together, and were looking for places in New York. Still, he remained tight-lipped about their relationship, explaining that he was taking Leslie's consideration into what he shares about the two.
"'Cause it's as much her relationship as it is mine and I can't speak for both of us," he noted. "But yeah, we are very, very happy. So that's what I'll say about that."
July 2017: Harington says he's very 'privileged' to share Game of Thrones legacy with Leslie
“I think that's the really special thing about it is that we met on this show and here we are seven years down the line back here promoting season seven,” Harington told ET. “I mean, it's mad. It's such a special thing. I'm so privileged.”
July 2017: Harington says Ygritte is the "only woman" for Jon
In an interview with Us Weekly, Harington made it clear that his Game of Thrones character's love story with Ygritte is the one that matters.
"No, Ygritte is the only woman for Jon. Always," he said when asked if Jon will ever have another love interest. "There will be no one else."
"MR. K.C. HARINGTON AND MISS R.E. LESLIE," it read. "The engagement is announced between, Kit, younger son of David and Deborah Harington of Worcestershire, and Rose, middle daughter of Sebastian and Candy Leslie of Aberdeenshire."
In an October interview on The Jonathan Ross Show, Harington revealed that he nearly ruined his proposal, deciding to forgo his extravagant plans and pop the question a day early.
"I was going to string up some lights in some trees and do all the romantic stuff," he revealed. "But we were in the country and we were under this beautiful night sky and had a log fire burning and red wine."
"I blew my load early," Harington confessed. "I was meant to do it the day after with the lights. What I meant to say was, I popped my question a bit early."
March 2018: Leslie gives a glimpse into her playful relationship with Harington
“I remember over the summer obviously the new episodes for the final season were coming through onto his iPad," she shared. "I can read his facial expressions. I don’t want to know anything that’s going on within his eyes, so I sent him packing. I kind of boot him out so that he can go to the coffee shop, because I can gauge. If he stiffens, it’s like, ‘Ooo someone’s dead.’ And then my mind goes off.”
She then revealed that Harington played an epic prank on her on April Fools’ Day the year prior, putting a replica of Jon Snow's severed head on the top shelf of their fridge for her to discover.
“I had just wrapped from season one of The Good Fight, so I had been in New York for about six months,” Leslie explained. “We hadn’t spent a lot of time together, and then I go home and the bastard puts this in the fridge.”
Harington told his own version of the story during his appearance on The Jonathan Ross Show.
“After that, she was in tears, and I was there going, ‘April Fools.’ It didn’t go down well,” he said with a smile. "She pretty much told me that if I did it ever again, that would be it, and I think that’s marriage included.”
Leslie laughed as she put her arm around Harington during the outing, the two later holding hands in the parking lot.
November 2018: The couple weathers cheating rumors
Harington quickly put any infidelity rumors to rest last November, when model Olga Vlasova claimed that she met Harington in Luxembourg, and alleged that they slept together multiple times before and after Harington tied the knot with Leslie in June. Harington's rep denied the claims to ET.
"The allegations in this story are completely false," his rep said. "[Harington] has never even been to Luxembourg nor has he ever met Olga Vlasova."
January 2019: Harington hints at having kids with Leslie
In an interview with GQ Australia, Harington talked about potentially having children with Leslie -- and how amazing it is that they would get to see a part of their parents' love story on-screen.
"It dawned on me, recently," Harington said. "And I have no idea if we will, but say me and Rose do have children. They'll know. They'll be able to see the genesis of their parents getting together. Which is quite a wonderful thought, really."
"I thank the show for everything," he continued. "But more than anything else, I thank it for introducing me to her."