The Sillem's Mountain Finch (Leucosticte sillemi) is a passerine bird only known from two specimens collected in the Karakoram mountain range in 1929 by Dutch ornithologist, Jerome Alexander Sillem.The specimens were of a small grey and white bird with a russet head, and were originally labelled as a type of Brandt's Mountain Finch (Leucosticte brandt) before Dutch ornithologist Kees Roselaar unearthed them from a drawer in the Amsterdam Zoological Museum in 1992 and realised they were a distinctive species in their own right.

After a period of 80 years the bird was rediscovered in June 2012, 1500 km to the east of the original 1929 sighting, by French photographer Yann Muzika whilst trekking in the Yenigou valley of Qinghai province in China.