The Supreme Leader is expected to celebrate the milestone with his family as he keeps members of the hermit kingdom’s leadership at arm’s length.
Unlike his father and grandfather, Kim – who is understood to turn 40 today – does not yet have a holiday assigned to his birthday.
Each year the occasion tends to pass with little to no mention in state media – and his date of birth has never been officially confirmed.
But according to the US government he was born on January 8, 1984.
Kim’s future has been under the microscope after naming his Gucci-loving 11-year-old daughter as his successor – while his increasingly bloated complexion has also sparked speculation about his health.
Expert Michael Madden, who runs North Korea Leadership Watch, said his birthday is likely to be a low-key affair.
He told The Sun: “We can assume with the highest degree of confidence that Kim Jong-un will have a dinner and note the occasion.
“There may well be some other recreation or activity planned like horseback riding, or maybe he will watch sports or play guitar and sing.”
Dumpy dictator Kim is a known horse lover – and previously released a bizarre propaganda video showing him galloping through a forest on a white horse and taking in a sunset while atop the pony.
But in recent weeks, puffy-faced Kim has appeared more and more bloated with a greyish complexion.
His weight has fluctuated massively in recent years – with pictures showing signs of dramatic weight loss in 2020, sparking a flurry of speculation about his health.
At his peak, Kim is believed to have had a bevy of health problems as the 5ft 6in tyrant is thought to have tipped the scales at over 22st.
His long list of reported health problems include hypertension, diabetes, elevated cholesterol and damage from years of chain smoking.
South Korea’s intelligence agency believe he may be suffering from insomnia as well as alcohol and nicotine dependency.
As he marks his birthday, Mr Madden told The Sun he’s likely to be receiving cortisone injections in his neck to relieve pressure for an unknown nerve or muscular condition.
Despite his health battles, Mr Madden said Kim, whose private life has long be shrouded in mystery, is expected to still indulge in a dinner.
But the guest list may be kept short.
He added: “The question is whether he has a dinner in a private setting with his family and some close associates, or if he stages a full-on liquor-and-wine-fuelled multi-course banquet and invites other North Korean elites and they have a proper celebration with singing and games and the like.
“Maybe he will do both.
“I would caution on the latter scenario because Kim Jong-un has become somewhat reticent when interacting with other members of the North Korean leadership.
“It appears there are new protocols when interacting with or approaching the leader at events and very elites actually engage him any more in impromptu conversation.
“So, he might stick with his family and close friends and avoid the Pyongyang party scene this year.”
Kim’s inner circle is akin to a revolving door, with the tyrant controlling it with an iron fist and purging those he no longer trusts.
It is understood Kim’s inner circle includes his sister, wife Ri Sol ju, brother Kim Jong-chul, daughter Ju-ae and his top generals – premier Kim Tok-hun, general Choe Ryong-hae and marshal Pak Jong-chon.
Rumours have also swirled Kim’s daughter could also be on the route to becoming a successor after he took her to several missile launches.
Despite the ruler’s love of grand displays of missile tests and military processions, his birthday is not celebrated like his late father or grandfather’s.
His father Kim Jong-il’s birthday is marked on February 16 on what’s known as the Day of the Shining Star, while his grandfather Kim Il Sung’s is remembered on April 15 with the so-called Day of the Sun.
Mr Madden said: “The only time I can recall that North Korean citizens were compelled to celebrate Kim Jong-un’s birthday was back in January 2010 when his hereditary succession drive was going full steam ahead.
“There have been accounts over the years that implicit reference to his birthday have come up in Party Cell meetings, but it has not yet become a holiday in the same fashion as his father or grandfather.”
KIM’S LEGENDARY APPETITE
INTELLIGENCE services and insiders have previously claimed Kim Jong-un is a prolific binge eater, drinker and smoker.
The Kim family’s ex-sushi chef Kenji Fujimoto has claimed the dictator once boasted he had consumed “10 bottles of Bordeaux” during a meal.
Kim is also reportedly absolutely crackers about Emmental cheese after developing a taste for it while studying in Switzerland as at teen.
Cheese and wine is not the only treats Kim, 36, enjoys however, with only the best being good enough for the North Korean leader as his people starve and live in poverty.
Kim’s staff reportedly brought along a host of high calorie and luxurious foods for their leader during his summit with US President Donald Trump in Vietnam in March 2019.
A team of personal chefs was also brought along to help tend to Kim – with the cook at Hanoi’s luxury Metropole saying they tasted dishes for an hour to make sure they were perfect for their leader.
Cavier and lobster are both also reportedly part of Kim’s palate, even though both are banned from being imported into North Korea by the United Nations.
Kim is also a fan of the delicacy shark fin soup, according to Mr Fujimoto.
Booze-loving Kim also reportedly likes to drink at least two bottles of Cristal Champagne per sitting, the chef said.
Bottles of the ritzy plonk can cost up to £7,500 – meaning Kim could drink away £15,000 during every meal.
Hundreds of thousands of bottle of cognac and vodka are also reportedly regularly imported to the Pyongyang, believed to be bound for Kim and the North Korea elite.
Kim is also reported to have pushed from a Western-style burger joint – such as a McDonald’s – to open in North Korea during talks with the US.
Kim allegedly hated being called fat – being dubbed Kim Fatty III in Chinese media.
North Korea officials reportedly made a state request to China to get them to drop the nickname.
Other insulting names used by Kim’s nearest ally include Kim Fat Fatty and Kim Abundant III.
Donald Trump even called Kim “short and fat” on Twitter as the two traded barbs before their string of high profile summits in 2018.
North Korea experts have previously claimed Kim’s weight is actually a well-cultivated ploy to make him look like his revered grandfather Kim Il-sung.
His grandad is also claimed to have been a gourmand, having cows fed beer and had them massaged to make the meat more tender.
Kim’s dad Kim Jong-il also died of a heart attack in 2011.
And while people may crack jokes about Kim’s weight battle, around 40% of North Korea’s population is undernourished.