Sunset at Montmajour – which depicts trees, bushes and sky – had spent years in a Norwegian private collector’s attic after he had been told the work was not by the Dutch master.
The museum said the painting was authenticated by letters, style and the physical materials used.
It is the first full-size canvas by Van Gogh discovered since 1928, reports BBC Online.
Museum director Axel Rueger called the discovery a ‘once-in-a-lifetime experience’ at an unveiling ceremony.
He said the institution had previously rejected the painting’s authenticity in the 1990s partly because it was not signed.
However thanks to new research techniques and a two-year investigation, it concluded the artwork was by the artist.
Researcher Teio Meedendorp said he and other researchers ‘found answers to all the key questions, which is remarkable for a painting that has been lost for more than 100 years’.
The piece can be dated to the exact day it was painted because the artist described it in a letter to his brother, Theo, saying he had painted it the previous day – on 4 July 1888.
He added he painted it ‘on a stony heath where small twisted oaks grow’.
The painting will be on display at the museum from 24 September.
-With New Age input
