Is leur in French masculine or feminine?

Answer 1

Leur is a possessive, but has no gender. It stands for "their". You can use it for females owning a feminine thing: Les filles sont retournées � leur voiture (the girls went back to their car), or for males owning a masculine-noun thing: les garçons cherchent leur ballon (the boys are looking for their balloon).
When it is written "leur", several people own a common thing (leur voiture: there are several girls, but they're all in the same car); the plural writing "leurs" indicate that there are several people, but also several things.

Answer 2

"Leur" is a possessive adjective in French that does not change in gender. It is used for both masculine and feminine nouns.