The fact was led to speculation in South Korean media about her identity.
The woman was shown on state TV on Sunday with the new leader at an official ceremony in honor of his late grandfather, Kim Il-Sung.
And on Saturday, the same woman was seen sitting next to Kim Jong-Un at a concert.
The appearances have made front-page news in South Korea.
Kim Jong-Un took power in the Communist state after the death of his father at the end of last year.
North Korean society is so closed to the outside world that no-one knows if Kim Jong-Un is married, or even his exact age.
So the appearance by his side of an elegant, black-clad, short-haired woman, probably in her 20s, has left many North and South Koreans playing guessing games.
Some South Korean news outlets suggested she might be his younger sister, Kim Yo-Jong, of whom very little is known, or even his wife.
On Sunday, the woman, dressed in a black jacket and skirt, was seen bowing with Kim Jong-Un, as part of a ceremony to mark the 18th anniversary of the death of Kim Il-Sung, the country’s founder.
She is believed to be the same woman shown by North Korea’s KRT broadcaster on Saturday walking into a concert behind Kim Jong-Un and sitting next to him.
A photo of the pair was also published in the North’s Rodong Sinmun newspaper on Monday, according to the Associated Press.
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