Nicknamed Yana, the female mammoth weighs more than 100 kilograms and is 120 centimetres tall.
Scientists believe that Yana was one year old when she died. Her remains are one of seven mammoth carcasses recovered worldwide.
Yana was found among the melting permafrost at the Batagaika crater in the far-eastern Russian area of Yakutia.
Known as the "gateway to the underworld", the crater is one kilometre deep and has previously revealed the remains of other ancient animals including bison, horses and dogs.
As permafrost melts, affected by climate change, more and more parts of prehistoric animals are being discovered.
Yana will be studied by scientists at Russia's North-Eastern Federal University, which has a dedicated mammoth research centre and museum.
The university described the find as "exceptional" and said it would give researchers new information about how mammoths lived and adapted to their surroundings.