In what parts of the world, besides the US, do endowed chairs exist? Browsing academia.SE, I discovered the existence of "endowed chairs" or "named chairs", i.e. professorships named in the honor of someone else and paid for by a donor with a gift to the university. I've never heard of anything like that before (I live and work in France so I mostly meet European academics).

Apart from the US (where this apparently exist), do endowed chairs exist elsewhere in the world?
Yes, endowed chairs exist outside the USA.

An example is the Lucasian Professor of Mathematics at the University of Cambridge, which (according to Wikipedia) was founded in 1663 by Henry Lucas, the then Member of Parliament for Cambridge. The post has been held by the likes of Isaac Newton, Paul Dirac and Stephen Hawking.